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https://issues.apache.org/jira/browse/PHOENIX-136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13976864#comment-13976864
]
ASF GitHub Bot commented on PHOENIX-136:
----------------------------------------
Github user maryannxue commented on a diff in the pull request:
https://github.com/apache/incubator-phoenix/pull/31#discussion_r11856917
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/compile/SubselectRewriter.java ---
@@ -0,0 +1,242 @@
+/*
+ * 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.
+ */
+
+package org.apache.phoenix.compile;
+
+import java.sql.SQLException;
+import java.sql.SQLFeatureNotSupportedException;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.phoenix.jdbc.PhoenixConnection;
+import org.apache.phoenix.parse.AliasedNode;
+import org.apache.phoenix.parse.ColumnParseNode;
+import org.apache.phoenix.parse.DerivedTableNode;
+import org.apache.phoenix.parse.HintNode;
+import org.apache.phoenix.parse.LimitNode;
+import org.apache.phoenix.parse.OrderByNode;
+import org.apache.phoenix.parse.ParseNode;
+import org.apache.phoenix.parse.ParseNodeRewriter;
+import org.apache.phoenix.parse.SelectStatement;
+import org.apache.phoenix.parse.TableNode;
+import org.apache.phoenix.parse.TableWildcardParseNode;
+import org.apache.phoenix.parse.WildcardParseNode;
+import org.apache.phoenix.util.SchemaUtil;
+
+import com.google.common.collect.Lists;
+
+public class SubselectRewriter extends ParseNodeRewriter {
+ private final String tableAlias;
+ private final Map<String, ParseNode> aliasMap;
+
+ public static SelectStatement applyPostFilters(SelectStatement
statement, List<ParseNode> postFilters, String subqueryAlias) throws
SQLException {
+ if (postFilters.isEmpty())
+ return statement;
+
+ // TODO handle this from caller
+ if (statement.getLimit() != null || (statement.isAggregate() &&
statement.getGroupBy().isEmpty()))
--- End diff --
Yes, limit with literal numbers in both outer and inner queries can be
handled. Please see "testDerivedTableWithLimit()".
Yes, agree. It would just require the compiler to handle derived tables.
Right now we only support cases that can be handled by "pre-processing", i.e.,
rewriting; and let QueryCompiler to throw a SQLFeatureNotSupportedException if
the from node is a derived table.
> Support derived tables
> ----------------------
>
> Key: PHOENIX-136
> URL: https://issues.apache.org/jira/browse/PHOENIX-136
> Project: Phoenix
> Issue Type: Task
> Reporter: James Taylor
> Assignee: James Taylor
> Labels: enhancement
>
> Add support for derived queries of the form:
> SELECT * FROM ( SELECT company, revenue FROM Company ORDER BY revenue) LIMIT
> 10
> Adding support for this requires a compile time change as well as a runtime
> execution change. The first version of the compile-time change could limit
> aggregation to only be allowed in the inner or the outer query, but not both.
> In this case, the inner and outer queries can be combined into a single query
> with the outer select becoming just a remapping of a subset of the projection
> from the inner select. The second version of the compile-time change could
> handle aggregation in the inner and outer select by performing client side
> (this is likely a less common scenario).
> For the runtime execution, change the UngroupedAggregateRegionObserver would
> be modified to look for a new "TopNLimit" attribute with an int value in the
> Scan. This would control the maximum number of values for the coprocessor to
> hold on to as the scan is performed. Then the
> GroupedAggregatingResultIterator would be modified to handle keeping the topN
> values received back from all the child iterators.
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