http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_index/indexing_guidelines.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_index/indexing_guidelines.html.md.erb b/geode-docs/developing/query_index/indexing_guidelines.html.md.erb deleted file mode 100644 index 88c14b0..0000000 --- a/geode-docs/developing/query_index/indexing_guidelines.html.md.erb +++ /dev/null @@ -1,41 +0,0 @@ ---- -title: Tips and Guidelines on Using Indexes ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -Optimizing your queries with indexes requires a cycle of careful planning, testing, and tuning. Poorly-defined indexes can degrade the performance of your queries instead of improving it. This section gives guidelines for index usage in the query service. - -<a id="indexing_guidelines__section_A8885DFC334243508C4563C9692E0801"></a> -When creating indexes, keep in mind the following: - -- Indexes incur maintenance costs as they must be updated when the indexed data changes. An index that requires many updates and is not used very often may require more system resources than using no index at all. -- Indexes consume memory. -- Indexes have limited support on overflow regions. See [Using Indexes with Overflow Regions](indexes_with_overflow_regions.html#concept_87BE7DB32C714EB0BF7532AF93569328) for details. -- If you are creating multiple indexes on the same region, first define your indexes and then create the indexes all at once to avoid iterating over the region multiple times. See [Creating Multiple Indexes at Once](create_multiple_indexes.html) for details. - -## <a id="indexing_guidelines__section_A8AFAA243B5C43DD9BB9F9235A48AF53" class="no-quick-link"></a>Tips for Writing Queries that Use Indexes - -As with query processors that run against relational databases, the way a query is written can greatly affect execution performance. Among other things, whether indexes are used depends on how each query is stated. These are some of the things to consider when optimizing your Geode queries for performance: - -- In general an index will improve query performance if the FROM clauses of the query and index match exactly. -- The query evaluation engine does not have a sophisticated cost-based optimizer. It has a simple optimizer which selects best index (one) or multiple indexes based on the index size and the operator that is being evaluated. -- For AND operators, you may get better results if the conditions that use indexes and conditions that are more selective come before other conditions in the query. -- Indexes are not used in expressions that contain NOT, so in a WHERE clause of a query, `qty >= 10` could have an index on `qty` applied for efficiency. However, `NOT(qty < 10)` could not have the same index applied. -- Whenever possible, provide a hint to allow the query engine to prefer a specific index. See [Using Query Index Hints](query_index_hints.html) -
http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_index/maintaining_indexes.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_index/maintaining_indexes.html.md.erb b/geode-docs/developing/query_index/maintaining_indexes.html.md.erb deleted file mode 100644 index 838f380..0000000 --- a/geode-docs/developing/query_index/maintaining_indexes.html.md.erb +++ /dev/null @@ -1,69 +0,0 @@ ---- -title: Maintaining Indexes (Synchronously or Asynchronously) and Index Storage ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -Indexes are automatically kept current with the region data they reference. The region attribute `IndexMaintenanceSynchronous` specifies whether the region indexes are updated synchronously when a region is modified or asynchronously in a background thread. - -## <a id="concept_98ED3F38919A490B9AE2553568455C35__section_FF1945F2AAFA4B158067CEE967410616" class="no-quick-link"></a>Index Maintenance Behavior - -Asynchronous index maintenance batches up multiple updates to the same region key. The default mode is synchronous, since this provides the greatest consistency with region data. - -See [RegionFactory.setIndexMaintenanceSynchronous](/releases/latest/javadoc/org/apache/geode/cache/RegionFactory.html). - -This declarative index creation sets the maintenance mode to asynchronous: - -``` pre -<region-attributes index-update-type="asynchronous"> -</region-attributes> -``` - -## <a id="concept_98ED3F38919A490B9AE2553568455C35__section_68308B5597CF4A9EAA8EC0BD83A233E6" class="no-quick-link"></a>Internal Index Structure and Storage - -Indexes are stored either as compact or non-compact data structures based on the indexed expression (even if the index key type is the same.) For example, consider the following Passenger object: - -``` pre -Passenger { - String name, - Date travelDate, - int age, - Flight flt, -} -Flight { - int flightId, - String origin, - String dest, -} -``` - -An index on the Passenger name field will have different memory space requirements in the cache than the Flight origin field even though they are both String field types. The internal data structure selected by Geode for index storage will depend on the field's level in the object. In this example, name is a top-level field and an index on name can be stored as a compact index. Since origin is a second-level field, any index that uses origin as the indexed expression will be stored as a non-compact index. - -**Compact Index** - -A compact index has simple data structures to minimize its footprint, at the expense of doing extra work at index maintenance. This index does not support the storage of projection attributes. - -Currently compact indexes are only selected only supports the creation of an index on a region path. In addition, the following conditions must be met: - -- Index maintenance is synchronous. -- The indexed expression is a path expression. -- The FROM clause has only one iterator. This implies that there is only one value in the index for each region entry and it is directly on the region values (not supported with keys, entries). - -**Non-Compact Index** - -Used whenever a compact index cannot be used. http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_index/query_index.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_index/query_index.html.md.erb b/geode-docs/developing/query_index/query_index.html.md.erb deleted file mode 100644 index 0f2c698..0000000 --- a/geode-docs/developing/query_index/query_index.html.md.erb +++ /dev/null @@ -1,79 +0,0 @@ ---- -title: Working with Indexes ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -The Geode query engine supports indexing. An index can provide significant performance gains for query execution. - -<a id="indexing__section_565C080FBDD0443C8504DF372E3C32C8"></a> -A query run without the aid of an index iterates through every object in the collection. If an index is available that matches part or all of the query specification, the query iterates only over the indexed set, and query processing time can be reduced. - -- **[Tips and Guidelines on Using Indexes](../../developing/query_index/indexing_guidelines.html)** - - Optimizing your queries with indexes requires a cycle of careful planning, testing, and tuning. Poorly-defined indexes can degrade the performance of your queries instead of improving it. This section gives guidelines for index usage in the query service. - -- **[Creating, Listing and Removing Indexes](../../developing/query_index/creating_an_index.html)** - - The Geode `QueryService` API provides methods to create, list and remove the index. You can also use `gfsh` command-line interface to create, list and remove indexes, and use cache.xml to create an index. - -- **[Creating Key Indexes](../../developing/query_index/creating_key_indexes.html)** - - Creating a key index is a good way to improve query performance when data is partitioned using a key or a field value. You can create key indexes by using the `createKeyIndex` method of the QueryService or by defining the index in `cache.xml`. Creating a key index makes the query service aware of the relationship between the values in the region and the keys in the region. - -- **[Creating Hash Indexes](../../developing/query_index/creating_hash_indexes.html)** - - Geode supports the creation of hash indexes for the purposes of performing equality-based queries. - -- **[Creating Indexes on Map Fields ("Map Indexes")](../../developing/query_index/creating_map_indexes.html)** - - To assist with the quick lookup of multiple values in a Map (or HashMap) type field, you can create an index (sometimes referred to as a "map index") on specific (or all) keys in that field. - -- **[Creating Multiple Indexes at Once](../../developing/query_index/create_multiple_indexes.html)** - - In order to speed and promote efficiency when creating indexes, you can define multiple indexes and then create them all at once. - -- **[Maintaining Indexes (Synchronously or Asynchronously) and Index Storage](../../developing/query_index/maintaining_indexes.html)** - - Indexes are automatically kept current with the region data they reference. The region attribute `IndexMaintenanceSynchronous` specifies whether the region indexes are updated synchronously when a region is modified or asynchronously in a background thread. - -- **[Using Query Index Hints](../../developing/query_index/query_index_hints.html)** - - You can use the hint keyword to allow Geode's query engine to prefer certain indexes. - -- **[Using Indexes on Single Region Queries](../../developing/query_index/indexes_on_single_region_queries.html)** - - Queries with one comparison operation may be improved with either a key or range index, depending on whether the attribute being compared is also the primary key. - -- **[Using Indexes with Equi-Join Queries](../../developing/query_index/using_indexes_with_equijoin_queries.html)** - - Equi-join queries are queries in which two regions are joined through an equality condition in the WHERE clause. - -- **[Using Indexes with Overflow Regions](../../developing/query_index/indexes_with_overflow_regions.html)** - - You can use indexes when querying on overflow regions; however, there are caveats. - -- **[Using Indexes on Equi-Join Queries using Multiple Regions](../../developing/query_index/using_indexes_with_equijoin_queries_multiple_regions.html)** - - To query across multiple regions, identify all equi-join conditions. Then, create as few indexes for the equi-join conditions as you can while still joining all regions. - -- **[Index Samples](../../developing/query_index/index_samples.html)** - - This topic provides code samples for creating query indexes. - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_index/query_index_hints.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_index/query_index_hints.html.md.erb b/geode-docs/developing/query_index/query_index_hints.html.md.erb deleted file mode 100644 index 9911014..0000000 --- a/geode-docs/developing/query_index/query_index_hints.html.md.erb +++ /dev/null @@ -1,40 +0,0 @@ ---- -title: Using Query Index Hints ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -You can use the hint keyword to allow Geode's query engine to prefer certain indexes. - -In cases where one index is hinted in a query, the query engine filters off the hinted index (if possible) and then iterates and filters from the resulting values. - -**Example:** - -``` pre -<HINT 'IDIndex'> SELECT * FROM /Portfolios p WHERE p.ID > 10 AND p.owner = 'XYZ' -``` - -If multiple indexes are added as hints, then the query engine will try to use as many indexes as possible while giving a preference for the hinted indexes. - -**Example:** - -``` pre -<HINT 'IDIndex', 'OwnerIndex'> SELECT * FROM /Portfolios p WHERE p.ID > 10 AND p.owner = 'XYZ' AND p.value < 100 -``` - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_index/using_indexes_with_equijoin_queries.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_index/using_indexes_with_equijoin_queries.html.md.erb b/geode-docs/developing/query_index/using_indexes_with_equijoin_queries.html.md.erb deleted file mode 100644 index a5ca840..0000000 --- a/geode-docs/developing/query_index/using_indexes_with_equijoin_queries.html.md.erb +++ /dev/null @@ -1,69 +0,0 @@ ---- -title: Using Indexes with Equi-Join Queries ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -Equi-join queries are queries in which two regions are joined through an equality condition in the WHERE clause. - -<a id="concept_A90C5FD84FCB45B2B28D6CE78DE1D117__section_47CFF4EF4D964FCFBB772B0347C02214"></a> -To use an index with an equi-join query: - -1. Create an index for each side of the equi-join condition. The query engine can quickly evaluate the query's equi-join condition by iterating over the keys of the left-side and right-side indexes for an equality match. - - **Note:** - Equi-join queries require regular indexes. Key indexes are not applied to equi-join queries. - - For this query: - - ``` pre - SELECT DISTINCT inv.name, ord.orderID, ord.status - FROM /investors inv, /orders ord - WHERE inv.investorID = ord.investorID - ``` - - Create two indexes: - - | FROM clause | Indexed expression | - |----------------|--------------------| - | /investors inv | inv.investorID | - | /orders ord | ord.investorID | - -2. If there are additional, single-region queries in a query with an equi-join condition, create additional indexes for the single-region conditions only if you are able to create at least one such index for each region in the query. Any indexing on a subset of the regions in the query will degrade performance. - - For this example query: - - ``` pre - SELECT DISTINCT * - FROM /investors inv, /securities sc, inv.heldSecurities inv_hs - WHERE sc.status = "active" - AND inv.name = "xyz" - AND inv.age > 75 - AND inv_hs.secName = sc.secName - ``` - - Create the indexes for the equi-join condition: - - | FROM clause | Indexed expression | - |--------------------------------------------|--------------------| - | /investors inv, inv.heldSecurities inv\_hs | inv\_hs.secName | - | /securities sc | sc.secName | - - Then, if you create any more indexes, create one on `sc.status` and one on `inv.age` or `inv.name` or both. - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_index/using_indexes_with_equijoin_queries_multiple_regions.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_index/using_indexes_with_equijoin_queries_multiple_regions.html.md.erb b/geode-docs/developing/query_index/using_indexes_with_equijoin_queries_multiple_regions.html.md.erb deleted file mode 100644 index 04e63d2..0000000 --- a/geode-docs/developing/query_index/using_indexes_with_equijoin_queries_multiple_regions.html.md.erb +++ /dev/null @@ -1,79 +0,0 @@ ---- -title: Using Indexes on Equi-Join Queries using Multiple Regions ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -To query across multiple regions, identify all equi-join conditions. Then, create as few indexes for the equi-join conditions as you can while still joining all regions. - -<a id="concept_DB2407C49F064B04AA58BC9D1DBA3666__section_70735ED43C4D47B0A19B910BB7E3A1DA"></a> -If there are equi-join conditions that redundantly join two regions (in order to more finely filter the data, for example), then creating redundant indexes for these joins will negatively impact performance. Create indexes only on one equi-join condition for each region pair. - -In this example query: - -``` pre -SELECT DISTINCT * -FROM /investors inv, /securities sc, /orders or, -inv.ordersPlaced inv_op, or.securities or_sec - WHERE inv_op.orderID = or.orderID - AND or_sec.secID = sc.secID -``` - -All conditions are required to join the regions, so you would create four indexes, two for each equi-join condition: - -| FROM clause | Indexed expression | -|------------------------------------------|--------------------| -| /investors inv, inv.ordersPlaced inv\_op | inv\_op.orderID | -| /orders or, or.securities or\_sec | or.orderID | - -| FROM clause | Indexed expression | -|-----------------------------------|--------------------| -| /orders or, or.securities or\_sec | or\_sec.secID | -| /securities sc | sc.secID | - -Adding another condition to the example: - -``` pre -SELECT DISTINCT * -FROM /investors inv, /securities sc, /orders or, -inv.ordersPlaced inv_op, or.securities or_sec, sc.investors sc_invs - WHERE inv_op.orderID = or.orderID - AND or_sec.secID = sc.secID - AND inv.investorID = sc_invs.investorID -``` - -You would still only want to use four indexes in all, as that's all you need to join all of the regions. You would need to choose the most performant two of the following three index pairs: - -| FROM clause | Indexed expression | -|------------------------------------------|--------------------| -| /investors inv, inv.ordersPlaced inv\_op | inv\_op.orderID | -| /orders or, or.securities or\_sec | or.orderID | - -| FROM clause | Indexed expression | -|---------------------------------------|--------------------| -| /orders or, or.securities or\_sec | or\_sec.secID | -| /securities sc, sc.investors sc\_invs | sc.secID | - -| FROM clause | Indexed expression | -|------------------------------------------|---------------------| -| /investors inv, inv.ordersPlaced inv\_op | inv.investorID | -| /securities sc, sc.investors sc\_invs | sc\_invs.investorID | - -The most performant set is that which narrows the data to the smallest result set possible. Examine your data and experiment with the three index pairs to see which provides the best performance. - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_select/aggregates.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_select/aggregates.html.md.erb b/geode-docs/developing/query_select/aggregates.html.md.erb deleted file mode 100644 index 38bd490..0000000 --- a/geode-docs/developing/query_select/aggregates.html.md.erb +++ /dev/null @@ -1,109 +0,0 @@ ---- -title: OQL Aggregate Functions ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -The aggregate functions -```MIN```, -```MAX```, -```AVG```, -```AVG``` over a DISTINCT expression, -```SUM``` over a DISTINCT expression, -```COUNT```, and -```COUNT``` over a DISTINCT expression -are supported. -The ```GROUP BY``` extension is also supported where appropriate. - -The ```MIN``` function returns the smallest of the selected -expression. -The type of the expression must evaluate to a -```java.lang.Comparable```. - -The ```MAX``` function returns the largest of the selected -expression. -The type of the expression must evaluate to a -```java.lang.Comparable```. - -The ```AVG``` function returns the arithmetic mean of the set -formed by the selected expression. -The type of the expression must evaluate to a -```java.lang.Number```. -For partitioned regions, -each node's buckets provide both a sum and the number of elements -to the node executing the query, -such that a correct average may be computed. - -The ```AVG``` function where the DISTINCT modifier is applied -to the expression returns the arithmetic mean of the set -of unique (distinct) values. -The type of the expression must evaluate to a -```java.lang.Number```. -For partitioned regions, -the distinct values in a node's buckets are returned -to the node executing the query. -The query node can then calculate the avarage over -the values that are unique across nodes, -after eliminating duplicate values that come from separate nodes. - -The ```SUM``` function returns the sum over the set -formed by the selected expression. -The type of the expression must evaluate to a -```java.lang.Number```. -For partitioned regions, -each node's buckets compute a sum over that node, -returning that sum -to the node executing the query, -when then sums across all nodes. - -The ```SUM``` function where the DISTINCT modifier is applied -to the expression returns the sum over the set -of unique (distinct) values. -The type of the expression must evaluate to a -```java.lang.Number```. -For partitioned regions, -the distinct values in a node's buckets are returned -to the node executing the query. -The query node can then calculate the sum over -the values that are unique across nodes, -after eliminating duplicate values that come from separate nodes. - -The ```COUNT``` function returns the quantity of values in the set -formed by the selected expression. -For example, to return the quantity of employees who have a -positive sales amount: - -``` pre -SELECT count(e.sales) FROM /employees e WHERE e.sales > 0.0 -``` - -The ```COUNT``` function where the DISTINCT modifier is applied -returns the quantity of unique (distinct) values in the set -formed by the selected expression. - -## GROUP BY Extension for Aggregate Functions - -```GROUP BY``` is required -when aggregate functions are used in combination -with other selected items. -It permits ordering. -For example, - -``` pre -SELECT ID, MAX(e.sales) FROM /employees e GROUP BY ID -``` http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_select/the_from_clause.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_select/the_from_clause.html.md.erb b/geode-docs/developing/query_select/the_from_clause.html.md.erb deleted file mode 100644 index 4490972..0000000 --- a/geode-docs/developing/query_select/the_from_clause.html.md.erb +++ /dev/null @@ -1,103 +0,0 @@ ---- -title: FROM Clause ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -<a id="the_from_clause__section_FAEBC02C4E414F91B1CA8D33E11218AF"></a> -Use the FROM clause to bring the data you need into scope for the rest of your query. The FROM clause also includes object typing and iterator variables. - -The query engine resolves names and path expressions according to the name space that is currently in scope in the query. - -## <a id="the_from_clause__section_CF6063A6C5134EFC89C43D106B6A6D4D" class="no-quick-link"></a>Path Expressions - -The initial name space for any query is composed of: - -- **Regions.** In the context of a query, the name of a region is specified by its full path starting with a forward slash ( / ) and delimited by the forward slash between region names. For example, **/exampleRegion** or **/root/exampleRegion**. -- **Region querying attributes**. From a region path, you can access the Region object's public fields and methods, referred to in querying as the region's attributes. For example, **/exampleRegion.size**. -- **Top-level region data.** You can access entry keys and entry data through the region path. - 1. `/exampleRegion.keySet` returns the Set of entry keys in the region - 2. `/exampleRegion.entryset` returns the Set of Region.Entry objects - 3. `/exampleRegion.values` returns the Collection of entry values - 4. `/exampleRegion` returns the Collection of entry values - -New name spaces are brought into scope based on the FROM clause in the SELECT statement. - -**Examples:** - -Query a region for all distinct values. Return a collection of unique entry values from the region: - -``` pre -SELECT DISTINCT * FROM /exampleRegion -``` - -Query the top level region data using entrySet. Return the keys and positions of Region.Entry objects whose mktValue attribute is greater than 25.00: - -``` pre -SELECT key, positions FROM /exampleRegion.entrySet, value.positions.values positions WHERE positions.mktValue >= 25.00 -``` - -Query the region for its entry values. Return a set of unique values from Region.Entry objects that have the key equal to 1: - -``` pre -SELECT DISTINCT entry.value FROM /exampleRegion.entries entry WHERE entry.key = '1' -``` - -Query the region for its entry values. Return the set of all entry values in which the `ID` field is greater than 1000: - -``` pre -SELECT * FROM /exampleRegion.entries entry WHERE entry.value.ID > 1000 -``` - -Query entry keys in the region. Return a set of entry keys in the region that have the key equal to '1': - -``` pre -SELECT * FROM /exampleRegion.keySet key WHERE key = '1' -``` - -Query values in the region. Return a collection of entry values in the region that have the status attribute value of 'active': - -``` pre -SELECT * FROM /exampleRegion.values portfolio WHERE portfolio.status = 'active' -``` - -## <a id="the_from_clause__section_AB1734C16DC348479C00FD6829B933AA" class="no-quick-link"></a>Aliases and Synonyms - -In query strings, you can use aliases in path expressions (region and its objects) so that you can refer to the region or objects in other places in the query. - -You can also use the **AS** keyword to provide a label for joined path expressions. - -**Examples:** - -``` pre -SELECT DISTINCT * FROM /exampleRegion p WHERE p.status = 'active' -``` - -``` pre -SELECT * FROM /exampleRegion p, p.positions.values AS pos WHERE pos.secId != '1' -``` - -## <a id="the_from_clause__section_A5B42CCB7C924949954AEC2DAAD51134" class="no-quick-link"></a>Object Typing - -Specifying object type in the FROM clause helps the query engine to process the query at optimal speed. Apart from specifying the object types during configuration (using key-constraint and value-constraint), type can be explicitly specified in the query string. - -**Example:** - -``` pre -SELECT DISTINCT * FROM /exampleRegion, positions.values positions TYPE Position WHERE positions.mktValue >= 25.00 -``` http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_select/the_import_statement.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_select/the_import_statement.html.md.erb b/geode-docs/developing/query_select/the_import_statement.html.md.erb deleted file mode 100644 index f58d443..0000000 --- a/geode-docs/developing/query_select/the_import_statement.html.md.erb +++ /dev/null @@ -1,31 +0,0 @@ ---- -title: IMPORT Statement ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -It is sometimes necessary for an OQL query to refer to the class of an object. In cases where the same class name resides in two different namescopes (packages), you must be able to differentiate the classes having the same name. - -The **IMPORT** statement is used to establish a name for a class in a query. - -``` pre -IMPORT package.Position; -SELECT DISTINCT * FROM /exampleRegion, positions.values positions TYPE Position WHERE positions.mktValue >= 25.00 -``` - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_select/the_select_statement.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_select/the_select_statement.html.md.erb b/geode-docs/developing/query_select/the_select_statement.html.md.erb deleted file mode 100644 index baaf6c1..0000000 --- a/geode-docs/developing/query_select/the_select_statement.html.md.erb +++ /dev/null @@ -1,220 +0,0 @@ ---- -title: SELECT Statement ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -The SELECT statement allows you to filter data from the collection of object(s) returned by a WHERE search operation. The projection list is either specified as \* or as a comma delimited list of expressions. - -For \*, the interim results of the WHERE clause are returned from the query. - -**Examples:** - -Query all objects from the region using \*. Returns the Collection of portfolios (The exampleRegion contains Portfolio as values). - -``` pre -SELECT * FROM /exampleRegion -``` - -Query secIds from positions. Returns the Collection of secIds from the positions of active portfolios: - -``` pre -SELECT secId FROM /exampleRegion, positions.values TYPE Position -WHERE status = 'active' -``` - -Returns a Collection of struct<type: String, positions: map> for the active portfolios. The second field of the struct is a Map ( jav.utils.Map ) object, which contains the positions map as the value: - -``` pre -SELECT "type", positions FROM /exampleRegion -WHERE status = 'active' -``` - -Returns a Collection of struct<portfolios: Portfolio, values: Position> for the active portfolios: - -``` pre -SELECT * FROM /exampleRegion, positions.values -TYPE Position WHERE status = 'active' -``` - -Returns a Collection of struct<pflo: Portfolio, posn: Position> for the active portfolios: - -``` pre -SELECT * FROM /exampleRegion portfolio, positions positions -TYPE Position WHERE portfolio.status = 'active' -``` - -## <a id="concept_85AE7D6B1E2941ED8BD2A8310A81753E__section_1B7762EC686A4808B1D12E8851954E82" class="no-quick-link"></a>SELECT Statement Results - -The result of a SELECT statement is either UNDEFINED or is a Collection that implements the [SelectResults](/releases/latest/javadoc/org/apache/geode/cache/query/SelectResults.html) interface. - -The SelectResults returned from the SELECT statement is either: - -1. A collection of objects, returned for these two cases: - - When only one expression is specified by the projection list and that expression is not explicitly specified using the fieldname:expression syntax - - When the SELECT list is \* and a single collection is specified in the FROM clause - -2. A collection of Structs that contains the objects - -When a struct is returned, the name of each field in the struct is determined following this order of preference: - -1. If a field is specified explicitly using the fieldname:expression syntax, the fieldname is used. -2. If the SELECT projection list is \* and an explicit iterator expression is used in the FROM clause, the iterator variable name is used as the field name. -3. If the field is associated with a region or attribute path, the last attribute name in the path is used. -4. If names cannot be decided based on these rules, arbitrary unique names are generated by the query processor. - -## <a id="concept_85AE7D6B1E2941ED8BD2A8310A81753E__section_972EE73A6F3E4427B6A99DB4EDF5860D" class="no-quick-link"></a>DISTINCT - -Use the DISTINCT keyword if you want to limit the results set to unique rows. Note that in the current version of Geode you are no longer required to use the DISTINCT keyword in your SELECT statement. - -``` pre -SELECT DISTINCT * FROM /exampleRegion -``` - -**Note:** -If you are using DISTINCT queries, you must implement the equals and hashCode methods for the objects that you query. - -## <a id="concept_85AE7D6B1E2941ED8BD2A8310A81753E__section_25D7055B33EC47B19B1B70264B39212F" class="no-quick-link"></a>LIMIT - -You can use the LIMIT keyword at the end of the query string to limit the number of values returned. - -For example, this query returns at most 10 values: - -``` pre -SELECT * FROM /exampleRegion LIMIT 10 -``` - -## <a id="concept_85AE7D6B1E2941ED8BD2A8310A81753E__section_D9DF0F785CA94EF8B367C3326CC12990" class="no-quick-link"></a>ORDER BY - -You can order your query results in ascending or descending order by using the ORDER BY clause. You must use DISTINCT when you write ORDER BY queries. - -``` pre -SELECT DISTINCT * FROM /exampleRegion WHERE ID < 101 ORDER BY ID -``` - -The following query sorts the results in ascending order: - -``` pre -SELECT DISTINCT * FROM /exampleRegion WHERE ID < 101 ORDER BY ID asc -``` - -The following query sorts the results in descending order: - -``` pre -SELECT DISTINCT * FROM /exampleRegion WHERE ID < 101 ORDER BY ID desc -``` - -**Note:** -If you are using ORDER BY queries, you must implement the equals and hashCode methods for the objects that you query. - -## <a id="concept_85AE7D6B1E2941ED8BD2A8310A81753E__section_69DCAD624E9640028BC86FD67649DEB2" class="no-quick-link"></a>Preset Query Functions - -Geode provides several built-in functions for evaluating or filtering data returned from a query. They include the following: - -<table> -<colgroup> -<col width="33%" /> -<col width="33%" /> -<col width="33%" /> -</colgroup> -<thead> -<tr class="header"> -<th>Function</th> -<th>Description</th> -<th>Example</th> -</tr> -</thead> -<tbody> -<tr class="odd"> -<td>ELEMENT(expr)</td> -<td>Extracts a single element from a collection or array. This function throws a <code class="ph codeph">FunctionDomainException</code> if the argument is not a collection or array with exactly one element.</td> -<td><pre class="pre codeblock"><code>ELEMENT(SELECT DISTINCT * - FROM /exampleRegion - WHERE id = 'XYZ-1').status = 'active'</code></pre></td> -</tr> -<tr class="even"> -<td>IS_DEFINED(expr)</td> -<td>Returns TRUE if the expression does not evaluate to UNDEFINED.</td> -<td><pre class="pre codeblock"><code>IS_DEFINED(SELECT DISTINCT * -FROM /exampleRegion p -WHERE p.status = 'active')</code></pre></td> -</tr> -<tr class="odd"> -<td>IS_UNDEFINED (expr)</td> -<td>Returns TRUE if the expression evaluates to UNDEFINED. In most queries, undefined values are not included in the query results. The IS_UNDEFINED function allows undefined values to be included, so you can identify element with undefined values.</td> -<td><pre class="pre codeblock"><code>SELECT DISTINCT * -FROM /exampleRegion p -WHERE IS_UNDEFINED(p.status)</code></pre></td> -</tr> -<tr class="even"> -<td>NVL(expr1, expr2)</td> -<td>Returns expr2 if expr1 is null. The expressions can be query parameters (bind arguments), path expressions, or literals.</td> -<td> </td> -</tr> -<tr class="odd"> -<td>TO_DATE(date_str, format_str)</td> -<td>Returns a Java Data class object. The arguments must be String S with date_str representing the date and format_str representing the format used by date_str. The format_str you provide is parsed using java.text.SimpleDateFormat.</td> -<td> </td> -</tr> -</tbody> -</table> - -## <a id="concept_85AE7D6B1E2941ED8BD2A8310A81753E__section_B2CBA00EB83F463DAF4769D7859C64C8" class="no-quick-link"></a>COUNT - -The COUNT keyword returns the number of results that match the query selection conditions specified in the WHERE clause. Using COUNT allows you to determine the size of a results set. The COUNT statement always returns an integer as its result. - -The following queries are example COUNT queries that return region entries: - -``` pre -SELECT COUNT(*) FROM /exampleRegion -``` - -``` pre -SELECT COUNT(*) FROM /exampleRegion WHERE ID > 0 -``` - -``` pre -SELECT COUNT(*) FROM /exampleRegion WHERE ID > 0 LIMIT 50 -``` - -``` pre -SELECT COUNT(*) FROM /exampleRegion -WHERE ID >0 AND status LIKE 'act%' -``` - -``` pre -SELECT COUNT(*) FROM /exampleRegion -WHERE ID IN SET(1,2,3,4,5) -``` - -The following COUNT query returns the total number of StructTypes that match the query's selection criteria. - -``` pre -SELECT COUNT(*) -FROM /exampleRegion p, p.positions.values pos -WHERE p.ID > 0 AND pos.secId 'IBM' -``` - -The following COUNT query uses the DISTINCT keyword and eliminates duplicates from the number of results. - -``` pre -SELECT DISTINCT COUNT(*) -FROM /exampleRegion p, p.positions.values pos -WHERE p.ID > 0 OR p.status = 'active' OR pos.secId -OR pos.secId = 'IBM' -``` http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/query_select/the_where_clause.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/query_select/the_where_clause.html.md.erb b/geode-docs/developing/query_select/the_where_clause.html.md.erb deleted file mode 100644 index 834bae9..0000000 --- a/geode-docs/developing/query_select/the_where_clause.html.md.erb +++ /dev/null @@ -1,353 +0,0 @@ ---- -title: WHERE Clause ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -<a id="the_where_clause__section_56BB3A7F44124CA9BFBC20E19399C6E4"></a> -Each FROM clause expression must resolve to a collection of objects. The collection is then available for iteration in the query expressions that follow in the WHERE clause. - -For example: - -``` pre -SELECT DISTINCT * FROM /exampleRegion p WHERE p.status = 'active' -``` - -The entry value collection is iterated by the WHERE clause, comparing the status field to the string 'active'. When a match is found, the value object of the entry is added to the return set. - -In the next example query, the collection specified in the first FROM clause expression is used by the rest of the SELECT statement, including the second FROM clause expression. - -``` pre -SELECT DISTINCT * FROM /exampleRegion, positions.values p WHERE p.qty > 1000.00 -``` - -## <a id="the_where_clause__section_99CA3FA508B740DCBAB4F01F8F9B1390" class="no-quick-link"></a>Implementing equals and hashCode Methods - -You must implement the `equals` and `hashCode` methods in your custom objects if you are doing ORDER BY and DISTINCT queries on the objects. The methods must conform to the properties and behavior documented in the online Java API documentation for `java.lang.Object`. Inconsistent query results may occur if these methods are absent. - -If you have implemented `equals` and `hashCode` methods in your custom objects, you must provide detailed implementations of these methods so that queries execute properly against the objects. For example, assume that you have defined a custom object (CustomObject) with the following variables: - -``` pre -int ID -int otherValue -``` - -Let's put two CustomObjects (we'll call them CustomObjectA and CustomObjectB) into the cache: - -CustomObjectA: - -``` pre -ID=1 -otherValue=1 -``` - -CustomObjectB: - -``` pre -ID=1 -otherValue=2 -``` - -If you have implemented the equals method to simply match on the ID field (ID == ID), queries will produce unpredictable results. - -The following query: - -``` pre -SELECT * FROM /CustomObjects c -WHERE c.ID > 1 AND c.ID < 3 -AND c.otherValue > 0 AND c.otherValue < 3 -``` - -returns two objects, however the objects will be two of either CustomObjectA or CustomObjectB. - -Alternately, the following query: - -``` pre -SELECT * FROM /CustomObjects c -WHERE c.ID > 1 AND c.ID < 3 -AND c.otherValue > 1 AND c.otherValue < 3 -``` - -returns either 0 results or 2 results of CustomObjectB, depending on which entry is evaluated last. - -To avoid unpredictable querying behavior, implement detailed versions of the `equals` and `hashCode` methods. - -If you are comparing a non-primitive field of the object in the WHERE clause, use the `equals` method instead of the `=` operator. For example instead of `nonPrimitiveObj = objToBeCompared` use `nonPrimitiveObj.equals(objToBeCompared)`. - -## <a id="the_where_clause__section_7484AD999D01473385628246697F37F6" class="no-quick-link"></a>Querying Serialized Objects - -Objects must implement serializable if you will be querying partitioned regions or if you are performing client-server querying. - -If you are using PDX serialization, you can access the values of individual fields without having to deserialize the entire object. This is accomplished by using PdxInstance, which is a wrapper around the serialized stream. The PdxInstance provides a helper method that takes field-name and returns the value without deserializing the object. While evaluating the query, the query engine will access field values by calling the getField method thus avoiding deserialization. - -To use PdxInstances in querying, ensure that PDX serialization reads are enabled in your server's cache. In gfsh, execute the following command before starting up your data members: - -``` pre -gfsh>configure pdx --read-serialized=true -``` - -See [configure pdx](../../tools_modules/gfsh/command-pages/configure.html#topic_jdkdiqbgphqh) for more information. - -In cache.xml, set the following: - -``` pre -// Cache configuration setting PDX read behavior -<cache> - <pdx read-serialized="true"> - ... - </pdx> -</cache> -``` - -## <a id="the_where_clause__section_75A114F9FEBF40A586621CAA1780DBD3" class="no-quick-link"></a>Attribute Visibility - -You can access any object or object attribute that is available in the current scope of a query. In querying, an object's attribute is any identifier that can be mapped to a public field or method in the object. In the FROM specification, any object that is in scope is valid. Therefore, at the beginning of a query, all locally cached regions and their attributes are in scope. - -For attribute Position.secId which is public and has getter method "getSecId()", the query can be written as the following: - -``` pre -SELECT DISTINCT * FROM /exampleRegion p WHERE p.position1.secId = '1' -SELECT DISTINCT * FROM /exampleRegion p WHERE p.position1.SecId = '1' -SELECT DISTINCT * FROM /exampleRegion p WHERE p.position1.getSecId() = '1' -``` - -The query engine tries to evaluate the value using the public field value. If a public field value is not found, it makes a get call using field name (note that the first character is uppercase.) - -## <a id="the_where_clause__section_EB7B976238104C0EACD959C52E5BD75B" class="no-quick-link"></a>Joins - -If collections in the FROM clause are not related to each other, the WHERE clause can be used to join them. - -The statement below returns all portfolios from the /exampleRegion and /exampleRegion2 regions that have the same status. - -``` pre -SELECT * FROM /exampleRegion portfolio1, /exampleRegion2 portfolio2 WHERE portfolio1.status = portfolio2.status -``` - -To create indexes for region joins you create single-region indexes for both sides of the join condition. These are used during query execution for the join condition. Partitioned regions do not support region joins. For more information on indexes, see [Working with Indexes](../query_index/query_index.html). - -**Examples:** - -Query two regions. Return the ID and status for portfolios that have the same status. - -``` pre -SELECT portfolio1.ID, portfolio2.status FROM /exampleRegion portfolio1, /exampleRegion2 portfolio2 WHERE portfolio1.status = portfolio2.status -``` - -Query two regions, iterating over all `positions` within each portfolio. Return all 4-tuples consisting of the value from each of the two regions and the value portion of the `positions` map from both regions in which the `secId` field of positions match. - -``` pre -SELECT * FROM /exampleRegion portfolio1, portfolio1.positions.values positions1, /exampleRegion2 portfolio2, portfolio2.positions.values positions2 WHERE positions1.secId = positions2.secId -``` - -Same query as the previous example, with the additional constraint that matches will have a `ID` of 1. - -``` pre -SELECT * FROM /exampleRegion portfolio1, portfolio1.positions.values positions1, /exampleRegion2 portfolio2, portfolio2.positions.values positions2 WHERE portfolio1.ID = 1 AND positions1.secId = positions2.secId -``` - -## <a id="the_where_clause__section_D91E0B06FFF6431490CC0BFA369425AD" class="no-quick-link"></a>LIKE - -Geode offers limited support for the LIKE predicate. LIKE can be used to mean 'equals to'. If you terminate the string with a wildcard ('%'), it behaves like 'starts with'. You can also place a wildcard (either '%' or '\_') at any other position in the comparison string. You can escape the wildcard characters to represent the characters themselves. - -**Note:** -The '\*' wildcard is not supported in OQL LIKE predicates. - -You can also use the LIKE predicate when an index is present. - -**Examples:** - -Query the region. Return all objects where status equals 'active': - -``` pre -SELECT * FROM /exampleRegion p WHERE p.status LIKE 'active' -``` - -Query the region using a wild card for comparison. Returns all objects where status begins with 'activ': - -``` pre -SELECT * FROM /exampleRegion p WHERE p.status LIKE 'activ%' -``` - -## Case Insensitive Fields - -You can use the Java String class methods `toUpperCase` and `toLowerCase` to transform fields where you want to perform a case-insensitive search. For example: - -``` pre -SELECT entry.value FROM /exampleRegion.entries entry WHERE entry.value.toUpperCase LIKE '%BAR%' -``` - -or - -``` pre -SELECT * FROM /exampleRegion WHERE foo.toLowerCase LIKE '%bar%' -``` - -## <a id="the_where_clause__section_D2F8D17B52B04895B672E2FCD675A676" class="no-quick-link"></a>Method Invocations - -To use a method in a query, use the attribute name that maps to the public method you want to invoke. - -``` pre -SELECT DISTINCT * FROM /exampleRegion p WHERE p.positions.size >= 2 - maps to positions.size() -``` - -Methods declared to return void evaluate to null when invoked through the query processor. - -You cannot invoke a static method. See [Enum Objects](the_where_clause.html#the_where_clause__section_59E7D64746AE495D942F2F09EF7DB9B5) for more information. - -**Methods without parameters** - -If the attribute name maps to a public method that takes no parameters, just include the method name in the query string as an attribute. For example, emps.isEmpty is equivalent to emps.isEmpty(). - -In the following example, the query invokes isEmpty on positions, and returns the set of all portfolios with no positions: - -``` pre -SELECT DISTINCT * FROM /exampleRegion p WHERE p.positions.isEmpty -``` - -**Methods with parameters** - -To invoke methods with parameters, include the method name in the query string as an attribute and provide method arguments between parentheses. - -This example passes the argument "Bo" to the public method, and returns all names that begin with "Bo". - -``` pre -SELECT DISTINCT * FROM /exampleRegion p WHERE p.name.startsWith('Bo') -``` - -For overloaded methods, the query processor decides which method to call by matching the runtime argument types with the parameter types required by the method. If only one method's signature matches the parameters provided, it is invoked. The query processor uses runtime types to match method signatures. - -If more than one method can be invoked, the query processor chooses the method whose parameter types are the most specific for the given arguments. For example, if an overloaded method includes versions with the same number of arguments, but one takes a Person type as an argument and the other takes an Employee type, derived from Person, Employee is the more specific object type. If the argument passed to the method is compatible with both types, the query processor uses the method with the Employee parameter type. - -The query processor uses the runtime types of the parameters and the receiver to determine the proper method to invoke. Because runtime types are used, an argument with a null value has no typing information, and so can be matched with any object type parameter. When a null argument is used, if the query processor cannot determine the proper method to invoke based on the non-null arguments, it throws an `AmbiguousNameException`. - -## <a id="the_where_clause__section_59E7D64746AE495D942F2F09EF7DB9B5" class="no-quick-link"></a>Enum Objects - -To write a query based on the value of an Enum object field, you must use the `toString` method of the enum object or use a query bind parameter. - -For example, the following query is NOT valid: - -``` pre -//INVALID QUERY -select distinct * from /QueryRegion0 where aDay = Day.Wednesday -``` - -The reason it is invalid is that the call to `Day.Wednesday` involves a static class and method invocation which is not supported. - -Enum types can be queried by using toString method of the enum object or by using bind parameter. When you query using the toString method, you must already know the constraint value that you wish to query. In the following first example, the known value is 'active'. - -**Examples:** - -Query enum type using the toString method: - -``` pre -// eStatus is an enum with values 'active' and 'inactive' -select * from /exampleRegion p where p.eStatus.toString() = 'active' -``` - -Query enum type using a bind parameter. The value of the desired Enum field ( Day.Wednesday) is passed as an execution parameter: - -``` pre -select distinct * from /QueryRegion0 where aDay = $1 -``` - -## <a id="the_where_clause__section_AC12146509F141378E493078540950C7" class="no-quick-link"></a>IN and SET - -The IN expression is a boolean indicating if one expression is present inside a collection of expressions of compatible type. The determination is based on the expressions' equals semantics. - -If `e1` and `e2` are expressions, `e2` is a collection, and `e1` is an object or a literal whose type is a subtype or the same type as the elements of `e2`, then `e1 IN e2` is an expression of type boolean. - -The expression returns: - -- TRUE if e1 is not UNDEFINED and is contained in collection e2 -- FALSE if e1 is not UNDEFINED and is not contained in collection e2 \# -- UNDEFINED if e1 is UNDEFINED - -For example, `2 IN SET(1, 2, 3)` is TRUE. - -Another example is when the collection you are querying into is defined by a subquery. This query looks for companies that have an active portfolio on file: - -``` pre -SELECT name, address FROM /company - WHERE id IN (SELECT id FROM /portfolios WHERE status = 'active') -``` - -The interior SELECT statement returns a collection of ids for all /portfolios entries whose status is active. The exterior SELECT iterates over /company, comparing each entryâs id with this collection. For each entry, if the IN expression returns TRUE, the associated name and address are added to the outer SELECTâs collection. - -**Comparing Set Values** - -The following is an example of a set value type comparison where sp is of type Set: - -``` pre -SELECT * FROM /exampleRegion WHERE sp = set('20','21','22') -``` - -In this case, if sp only contains '20' and '21', then the query will evalute to false. The query compares the two sets and looks for the presence of all elements in both sets. - -For other collections types like list, the query can be written as follows: - -``` pre -SELECT * FROM /exampleRegion WHERE sp.containsAll(set('20','21','22)) -``` - -where sp is of type List. - -In order to use it for Set value, the query can be written as: - -``` pre -SELECT * FROM /exampleRegion WHERE sp IN SET (set('20','21','22'),set('10',11','12')) -``` - -where a set value is searched in collection of set values. - -One problem is that you cannot create indexes on Set or List types (collection types) that are not comparable. To workaround this, you can create an index on a custom collection type that implements Comparable. - -## <a id="the_where_clause__section_E7206D045BEC4F67A8D2B793922BF213" class="no-quick-link"></a>Double.NaN and Float.NaN Comparisons - -The comparison behavior of Double.NaN and Float.NaN within Geode queries follow the semantics of the JDK methods Float.compareTo and Double.compareTo. - -In summary, the comparisons differ in the following ways from those performed by the Java language numerical comparison operators (<, <=, ==, >= >) when applied to primitive double [float] values: - -- Double.NaN \[Float.NaN\] is considered to be equal to itself and greater than all other double \[float\] values (including Double.POSITIVE\_INFINITY \[Float.POSITIVE\_INFINITY\]). -- 0.0d \[0.0f\] is considered by this method to be greater than -0.0d \[-0.0f\]. - -Therefore, Double.NaN\[Float.NaN\] is considered to be larger than Double.POSITIVE\_INFINITY\[Float.POSITIVE\_INFINITY\]. Here are some example queries and what to expect. - -| If p.value is NaN, the following query: | Evaluates to: | Appears in the result set? | -|------------------------------------------------------------------------------------------------|-------------------|--------------------------------| -| `SELECT * FROM /positions p WHERE p.value = 0` | false | no | -| `SELECT * FROM /positions p WHERE p.value > 0` | true | yes | -| `SELECT * FROM /positions p WHERE p.value >= 0` | true | yes | -| `SELECT * FROM /positions p WHERE p.value < 0` | false | no | -| `SELECT * FROM /positions p WHERE p.value <= 0` | false | no | -| **When p.value and p.value1 are both NaN, the following query:** | **Evaluates to:** | **Appears in the result set:** | -| `SELECT * FROM /positions p WHERE p.value = p.value1 ` | true | yes | - -If you combine values when defining the following query in your code, when the query is executed the value itself is considered UNDEFINED when parsed and will not be returned in the result set. - -``` pre -String query = "SELECT * FROM /positions p WHERE p.value =" + Float.NaN -``` - -Executing this query, the value itself is considered UNDEFINED when parsed and will not be returned in the result set. - -To retrieve NaN values without having another field already stored as NaN, you can define the following query in your code: - -``` pre -String query = "SELECT * FROM /positions p WHERE p.value > " + Float.MAX_VALUE; - -``` http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/chapter_overview.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/chapter_overview.html.md.erb b/geode-docs/developing/querying_basics/chapter_overview.html.md.erb deleted file mode 100644 index 328cc46..0000000 --- a/geode-docs/developing/querying_basics/chapter_overview.html.md.erb +++ /dev/null @@ -1,38 +0,0 @@ ---- -title: Querying ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -Geode provides a SQL-like querying language called OQL that allows you to access data stored in Geode regions. - -Since Geode regions are key-value stores where values can range from simple byte arrays to complex nested objects, Geode uses a query syntax based on OQL (Object Query Language) to query region data. OQL is very similar to SQL, but OQL allows you to query complex objects, object attributes, and methods. - -- **[Geode Querying FAQ and Examples](../../getting_started/querying_quick_reference.html)** - - This topic answers some frequently asked questions on querying functionality. It provides examples to help you get started with Geode querying. - -- **[Basic Querying](../../developing/querying_basics/query_basics.html)** - - This section provides a high-level introduction to Geode querying such as building a query string and describes query language features. - -- **[Advanced Querying](../../developing/query_additional/advanced_querying.html)** - - This section includes advanced querying topics such as using query indexes, using query bind parameters, querying partitioned regions and query debugging. - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/comments_in_query_strings.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/comments_in_query_strings.html.md.erb b/geode-docs/developing/querying_basics/comments_in_query_strings.html.md.erb deleted file mode 100644 index d55bb3f..0000000 --- a/geode-docs/developing/querying_basics/comments_in_query_strings.html.md.erb +++ /dev/null @@ -1,30 +0,0 @@ ---- -title: Comments in Query Strings ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -Comment lines being with `--` (double dash). Comment blocks begin with `/*` and end with `*/`. For example: - -``` pre -SELECT * --my comment -FROM /exampleRegion /* here is -a comment */ WHERE status = âactiveâ -``` - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/monitor_queries_for_low_memory.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/monitor_queries_for_low_memory.html.md.erb b/geode-docs/developing/querying_basics/monitor_queries_for_low_memory.html.md.erb deleted file mode 100644 index 6d065c0..0000000 --- a/geode-docs/developing/querying_basics/monitor_queries_for_low_memory.html.md.erb +++ /dev/null @@ -1,41 +0,0 @@ ---- -title: Monitoring Queries for Low Memory ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -<a id="topic_685CED6DE7D0449DB8816E8ABC1A6E6F"></a> - - -The query monitoring feature prevents out-of-memory exceptions from occurring when you execute queries or create indexes. - -This feature is automatically enabled when you set a `critical-heap-percentage` attribute for the resource-manager element in cache.xml or by using the `cache.getResourceManager().setCriticalHelpPercentage(float heapPercentage)` API. Use this feature to cancel out queries that are taking too long and to warn the user that there are low memory conditions when they are running queries or creating indexes. - -You can override this feature by setting the system property `gemfire.cache.DISABLE_QUERY_MONITOR_FOR_LOW_MEMORY` to true. - -When the query memory monitoring feature is on, the default query time out is set to five hours. You can override this value by setting a larger or smaller, non -1 value to the existing query time out system variable `gemfire.cache.MAX_QUERY_EXECUTION_TIME`. - -When system memory is low (as determined by the critical heap percentage threshold that you defined in cache.xml or in the getResourceManager API ), queries will throw a `QueryExecutionLowMemoryException`. Any indexes that are in the process of being created will throw an `InvalidIndexException` with the message indicating the reason. - -## <a id="topic_685CED6DE7D0449DB8816E8ABC1A6E6F__section_2E9DEEC9D9C94D038543DDE03BC60B20" class="no-quick-link"></a>Partitioned Region Queries and Low Memory - -Partitioned region queries are likely causes for out-of-memory exceptions. If query monitoring is enabled, partitioned region queries drop or ignore results that are being gathered by other servers if the executing server is low in memory. - -Query-monitoring does not address a scenario in which a low-level collection is expanded while the partitioned region query is gathering results. For example, if a row is added and then causes a Java level collection or array to expand, it is possible to then encounter an out-of-memory exception. This scenario is rare and is only possible if the collection size itself expands before a low memory condition is met and then expands beyond the remaining available memory. As a workaround, in the event that you encounter this situation, you may be able to tune the system by additionally lowering the `critical-heap-percentage`. - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/oql_compared_to_sql.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/oql_compared_to_sql.html.md.erb b/geode-docs/developing/querying_basics/oql_compared_to_sql.html.md.erb deleted file mode 100644 index 8b4d7f9..0000000 --- a/geode-docs/developing/querying_basics/oql_compared_to_sql.html.md.erb +++ /dev/null @@ -1,31 +0,0 @@ ---- -title: Advantages of OQL ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -The following list describes some of the advantages of using an OQL-based querying language: - -- You can query on any arbitrary object -- You can navigate object collections -- You can invoke methods and access the behavior of objects -- Data mapping is supported -- You are not required to declare types. Since you do not need type definitions, you can work across multiple languages -- You are not constrained by a schema - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/performance_considerations.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/performance_considerations.html.md.erb b/geode-docs/developing/querying_basics/performance_considerations.html.md.erb deleted file mode 100644 index 4e19250..0000000 --- a/geode-docs/developing/querying_basics/performance_considerations.html.md.erb +++ /dev/null @@ -1,33 +0,0 @@ ---- -title: Performance Considerations ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -This topic covers considerations for improving query performance. - -<a id="performance_considerations__section_2DA52BD8C72A4D01982CA8A44954ADAF"></a> -Some general performance tips: - -- Improve query performance whenever possible by creating indexes. See [Tips and Guidelines on Using Indexes](../query_index/indexing_guidelines.html#indexing_guidelines) for some scenarios for using indexes. -- Use bind parameters for frequently used queries. When you use a bind parameter, the query is compiled once. This improves the subsequent performance of the query when it is re-run. See [Using Query Bind Parameters](../query_additional/using_query_bind_parameters.html#concept_173E775FE46B47DF9D7D1E40680D34DF) for more details. -- When querying partitioned regions, execute the query using the FunctionService. This function allows you to target a particular node, which will improve performance greatly by avoiding query distribution. See [Querying a Partitioned Region on a Single Node](../query_additional/query_on_a_single_node.html#concept_30B18A6507534993BD55C2C9E0544A97) for more information. -- Use key indexes when querying data that has been partitioned by a key or field value. See [Optimizing Queries on Data Partitioned by a Key or Field Value](../query_additional/partitioned_region_key_or_field_value.html#concept_3010014DFBC9479783B2B45982014454). -- The size of a query result set depends on the restrictiveness of the query and the size of the total data set. A partitioned region can hold much more data than other types of regions, so there is more potential for larger result sets on partitioned region queries. This could cause the member receiving the results to run out of memory if the result set is very large. - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/query_basics.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/query_basics.html.md.erb b/geode-docs/developing/querying_basics/query_basics.html.md.erb deleted file mode 100644 index 4121140..0000000 --- a/geode-docs/developing/querying_basics/query_basics.html.md.erb +++ /dev/null @@ -1,57 +0,0 @@ ---- -title: Basic Querying ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -This section provides a high-level introduction to Geode querying such as building a query string and describes query language features. - -<a id="querying_with_oql__section_828A9660B5014DCAA883A58A45E6B51A"></a> -Geode provides a SQL-like querying language that allows you to access data stored in Geode regions. Since Geode regions are key-value stores where values can range from simple byte arrays to complex nested objects, Geode uses a query syntax based on OQL (Object Query Language) to query region data. OQL and SQL have many syntactical similarities, however they have significant differences. For example, while OQL does not offer all of the capabilities of SQL like aggregates, OQL does allow you to execute queries on complex object graphs, query object attributes and invoke object methods. - -The syntax of a typical Geode OQL query is: - -``` pre -[IMPORT package] -SELECT [DISTINCT] projectionList -FROM collection1, [collection2, â¦] -[WHERE clause] -[ORDER BY order_criteria [desc]] -``` - -Therefore, a simple Geode OQL query resembles the following: - -``` pre -SELECT DISTINCT * FROM /exampleRegion WHERE status = âactiveâ -``` - -An important characteristic of Geode querying to note is that by default, Geode queries on the values of a region and not on keys. To obtain keys from a region, you must use the keySet path expression on the queried region. For example, `/exampleRegion.keySet`. - -For those new to the Geode querying, see also the [Geode Querying FAQ and Examples](../../getting_started/querying_quick_reference.html#reference_D5CE64F5FD6F4A808AEFB748C867189E). - -- **[Advantages of OQL](../../developing/querying_basics/oql_compared_to_sql.html)** - -- **[Writing and Executing a Query in Geode](../../developing/querying_basics/running_a_query.html)** - -- **[Building a Query String](../../developing/querying_basics/what_is_a_query_string.html)** - -- **[OQL Syntax and Semantics](../../developing/query_additional/query_language_features.html)** - -- **[Query Language Restrictions and Unsupported Features](../../developing/querying_basics/restrictions_and_unsupported_features.html)** - - http://git-wip-us.apache.org/repos/asf/incubator-geode/blob/84cfbdfc/geode-docs/developing/querying_basics/query_grammar_and_reserved_words.html.md.erb ---------------------------------------------------------------------- diff --git a/geode-docs/developing/querying_basics/query_grammar_and_reserved_words.html.md.erb b/geode-docs/developing/querying_basics/query_grammar_and_reserved_words.html.md.erb deleted file mode 100644 index b653a07..0000000 --- a/geode-docs/developing/querying_basics/query_grammar_and_reserved_words.html.md.erb +++ /dev/null @@ -1,163 +0,0 @@ ---- -title: Query Language Grammar ---- - -<!-- -Licensed to the Apache Software Foundation (ASF) under one or more -contributor license agreements. See the NOTICE file distributed with -this work for additional information regarding copyright ownership. -The ASF licenses this file to You under the Apache License, Version 2.0 -(the "License"); you may not use this file except in compliance with -the License. You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - -Unless required by applicable law or agreed to in writing, software -distributed under the License is distributed on an "AS IS" BASIS, -WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -See the License for the specific language governing permissions and -limitations under the License. ---> - -## <a id="query_grammar_and_reserved_words__section_F6DF7EBA0201463F9F19645849748D54" class="no-quick-link"></a>Language Grammar - -Notation used in the grammar: -n -A nonterminal symbol that has to appear at some place within the grammar on the left side of a rule. All nonterminal symbols have to be derived to be terminal symbols. - - ***t*** -A terminal symbol (shown in italic bold). - -x y -x followed by y - -x | y -x or y - -(x | y) -x or y - -\[ x \] -x or empty - -{ x } -A possibly empty sequence of x. - - *comment* -descriptive text - -Grammar list: - -``` pre -symbol ::= expression -query_program ::= [ imports semicolon ] query [semicolon] -imports ::= import { semicolon import } -import ::= IMPORT qualifiedName [ AS identifier ] -query ::= selectExpr | expr -selectExpr ::= SELECT DISTINCT projectionAttributes fromClause [ whereClause ] -projectionAttributes ::= * | projectionList -projectionList ::= projection { comma projection } -projection ::= field | expr [ AS identifier ] -field ::= identifier colon expr -fromClause ::= FROM iteratorDef { comma iteratorDef } -iteratorDef ::= expr [ [ AS ] identifier ] [ TYPE identifier ] | identifier IN expr [ TYPE identifier ] -whereClause ::= WHERE expr -expr ::= castExpr -castExpr ::= orExpr | left_paren identifier right_paren castExpr -orExpr ::= andExpr { OR andExpr } -andExpr ::= equalityExpr { AND equalityExpr } -equalityExpr ::= relationalExpr { ( = | <> | != ) relationalExpr } -relationalExpr ::= inExpr { ( < | <= | > | >= ) inExpr } -inExpr ::= unaryExpr { IN unaryExpr } -unaryExpr ::= [ NOT ] unaryExpr -postfixExpr ::= primaryExpr { left_bracket expr right_bracket } - | primaryExpr { dot identifier [ argList ] } -argList ::= left_paren [ valueList ] right_paren -qualifiedName ::= identifier { dot identifier } -primaryExpr ::= functionExpr - | identifier [ argList ] - | undefinedExpr - | collectionConstruction - | queryParam - | literal - | ( query ) - | region_path -functionExpr ::= ELEMENT left_paren query right_paren - | NVL left_paren query comma query right_paren - | TO_DATE left_paren query right_paren -undefinedExpr ::= IS_UNDEFINED left_paren query right_paren - | IS_DEFINED left_paren query right_paren -collectionConstruction ::= SET left_paren [ valueList ] right_paren -valueList ::= expr { comma expr } -queryParam ::= $ integerLiteral -region_path ::= forward_slash region_name { forward_slash region_name } -region_name ::= name_character { name_character } -identifier ::= letter { name_character } -literal ::= booleanLiteral - | integerLiteral - | longLiteral - | doubleLiteral - | floatLiteral - | charLiteral - | stringLiteral - | dateLiteral - | timeLiteral - | timestampLiteral - | NULL - | UNDEFINED -booleanLiteral ::= TRUE | FALSE -integerLiteral ::= [ dash ] digit { digit } -longLiteral ::= integerLiteral L -floatLiteral ::= [ dash ] digit { digit } dot digit { digit } [ ( E | e ) [ plus | dash ] digit { digit } ] F -doubleLiteral ::= [ dash ] digit { digit } dot digit { digit } [ ( E | e ) [ plus | dash ] digit { digit } ] [ D ] -charLiteral ::= CHAR single_quote character single_quote -stringLiteral ::= single_quote { character } single_quote -dateLiteral ::= DATE single_quote integerLiteral dash integerLiteral dash integerLiteral single_quote -timeLiteral ::= TIME single_quote integerLiteral colon - integerLiteral colon integerLiteral single_quote -timestampLiteral ::= TIMESTAMP single_quote - integerLiteral dash integerLiteral dash integerLiteral integerLiteral colon - integerLiteral colon - digit { digit } [ dot digit { digit } ] single_quote -letter ::= any unicode letter -character ::= any unicode character except 0xFFFF -name_character ::= letter | digit | underscore -digit ::= any unicode digit -``` - -The expressions in the following are all terminal characters: - -``` pre -dot ::= . -left_paren ::= ( -right_paren ::= ) -left_bracket ::= [ -right_bracket ::= ] -single_quote ::= â -underscore ::= _ -forward_slash ::= / -comma ::= , -semicolon ::= ; -colon ::= : -dash ::= - -plus ::= + - -``` - -## <a id="query_grammar_and_reserved_words__section_B074373F2ED44DC7B98652E70ABC5D5D" class="no-quick-link"></a>Language Notes - -- Query language keywords such as SELECT, NULL, and DATE are case-insensitive. Identifiers such as attribute names, method names, and path expressions are case-sensitive. -- Comment lines begin with -- (double dash). -- Comment blocks begin with /\* and end with \*/. -- String literals are delimited by single-quotes. Embedded single-quotes are doubled. - - Examples: - - ``` pre - 'Hello' value = Hello - 'He said, ''Hello''' value = He said, 'Hello' - ``` - -- Character literals begin with the CHAR keyword followed by the character in single quotation marks. The single-quotation mark character itself is represented as `CHAR ''''` (with four single quotation marks). -- In the TIMESTAMP literal, there is a maximum of nine digits after the decimal point. -
