http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/3be0f122/docs/topics/impala_ddl.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_ddl.xml b/docs/topics/impala_ddl.xml new file mode 100644 index 0000000..8e6a3bd --- /dev/null +++ b/docs/topics/impala_ddl.xml @@ -0,0 +1,150 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> +<concept id="ddl"> + + <title>DDL Statements</title> + <prolog> + <metadata> + <data name="Category" value="Impala"/> + <data name="Category" value="SQL"/> + <data name="Category" value="DDL"/> + <data name="Category" value="Data Analysts"/> + <data name="Category" value="Developers"/> + <data name="Category" value="Schemas"/> + <data name="Category" value="Tables"/> + <data name="Category" value="Databases"/> + </metadata> + </prolog> + + <conbody> + + <p> + DDL refers to <q>Data Definition Language</q>, a subset of SQL statements that change the structure of the + database schema in some way, typically by creating, deleting, or modifying schema objects such as databases, + tables, and views. Most Impala DDL statements start with the keywords <codeph>CREATE</codeph>, + <codeph>DROP</codeph>, or <codeph>ALTER</codeph>. + </p> + + <p> + The Impala DDL statements are: + </p> + + <ul> + <li> + <xref href="impala_alter_table.xml#alter_table"/> + </li> + + <li> + <xref href="impala_alter_view.xml#alter_view"/> + </li> + + <li> + <xref href="impala_compute_stats.xml#compute_stats"/> + </li> + + <li> + <xref href="impala_create_database.xml#create_database"/> + </li> + + <li> + <xref href="impala_create_function.xml#create_function"/> + </li> + + <li rev="2.0.0"> + <xref href="impala_create_role.xml#create_role"/> + </li> + + <li> + <xref href="impala_create_table.xml#create_table"/> + </li> + + <li> + <xref href="impala_create_view.xml#create_view"/> + </li> + + <li> + <xref href="impala_drop_database.xml#drop_database"/> + </li> + + <li> + <xref href="impala_drop_function.xml#drop_function"/> + </li> + + <li rev="2.0.0"> + <xref href="impala_drop_role.xml#drop_role"/> + </li> + + <li> + <xref href="impala_drop_table.xml#drop_table"/> + </li> + + <li> + <xref href="impala_drop_view.xml#drop_view"/> + </li> + + <li rev="2.0.0"> + <xref href="impala_grant.xml#grant"/> + </li> + + <li rev="2.0.0"> + <xref href="impala_revoke.xml#revoke"/> + </li> + </ul> + + <p> + After Impala executes a DDL command, information about available tables, columns, views, partitions, and so + on is automatically synchronized between all the Impala nodes in a cluster. (Prior to Impala 1.2, you had to + issue a <codeph>REFRESH</codeph> or <codeph>INVALIDATE METADATA</codeph> statement manually on the other + nodes to make them aware of the changes.) + </p> + + <p> + If the timing of metadata updates is significant, for example if you use round-robin scheduling where each + query could be issued through a different Impala node, you can enable the + <xref href="impala_sync_ddl.xml#sync_ddl">SYNC_DDL</xref> query option to make the DDL statement wait until + all nodes have been notified about the metadata changes. + </p> + + <p rev="2.2.0"> + See <xref href="impala_s3.xml#s3"/> for details about how Impala DDL statements interact with + tables and partitions stored in the Amazon S3 filesystem. + </p> + + <p> + Although the <codeph>INSERT</codeph> statement is officially classified as a DML (data manipulation language) + statement, it also involves metadata changes that must be broadcast to all Impala nodes, and so is also + affected by the <codeph>SYNC_DDL</codeph> query option. + </p> + + <p> + Because the <codeph>SYNC_DDL</codeph> query option makes each DDL operation take longer than normal, you + might only enable it before the last DDL operation in a sequence. For example, if you are running a script + that issues multiple of DDL operations to set up an entire new schema, add several new partitions, and so on, + you might minimize the performance overhead by enabling the query option only before the last + <codeph>CREATE</codeph>, <codeph>DROP</codeph>, <codeph>ALTER</codeph>, or <codeph>INSERT</codeph> statement. + The script only finishes when all the relevant metadata changes are recognized by all the Impala nodes, so + you could connect to any node and issue queries through it. + </p> + + <p> + The classification of DDL, DML, and other statements is not necessarily the same between Impala and Hive. + Impala organizes these statements in a way intended to be familiar to people familiar with relational + databases or data warehouse products. Statements that modify the metastore database, such as <codeph>COMPUTE + STATS</codeph>, are classified as DDL. Statements that only query the metastore database, such as + <codeph>SHOW</codeph> or <codeph>DESCRIBE</codeph>, are put into a separate category of utility statements. + </p> + + <note> + The query types shown in the Impala debug web user interface might not match exactly the categories listed + here. For example, currently the <codeph>USE</codeph> statement is shown as DDL in the debug web UI. The + query types shown in the debug web UI are subject to change, for improved consistency. + </note> + + <p conref="../shared/impala_common.xml#common/related_info"/> + + <p> + The other major classifications of SQL statements are data manipulation language (see + <xref href="impala_dml.xml#dml"/>) and queries (see <xref href="impala_select.xml#select"/>). + </p> + </conbody> +</concept>
http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/3be0f122/docs/topics/impala_debug_action.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_debug_action.xml b/docs/topics/impala_debug_action.xml new file mode 100644 index 0000000..977cbe0 --- /dev/null +++ b/docs/topics/impala_debug_action.xml @@ -0,0 +1,33 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> +<concept id="debug_action"> + + <title>DEBUG_ACTION Query Option</title> + <titlealts audience="PDF"><navtitle>DEBUG_ACTION</navtitle></titlealts> + <prolog> + <metadata> + <data name="Category" value="Impala"/> + <data name="Category" value="Impala Query Options"/> + <data name="Category" value="Querying"/> + <data name="Category" value="Developers"/> + <data name="Category" value="Administrators"/> + <data name="Category" value="Troubleshooting"/> + </metadata> + </prolog> + + <conbody> + + <p> + <indexterm audience="Cloudera">DEBUG_ACTION query option</indexterm> + Introduces artificial problem conditions within queries. For internal Cloudera debugging and troubleshooting. + </p> + + <p> + <b>Type:</b> <codeph>STRING</codeph> + </p> + + <p> + <b>Default:</b> empty string + </p> + </conbody> +</concept> http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/3be0f122/docs/topics/impala_decimal.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_decimal.xml b/docs/topics/impala_decimal.xml new file mode 100644 index 0000000..58958ab --- /dev/null +++ b/docs/topics/impala_decimal.xml @@ -0,0 +1,817 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> +<concept rev="1.4.0" id="decimal"> + + <title>DECIMAL Data Type (<keyword keyref="impala14"/> or higher only)</title> + <titlealts audience="PDF"><navtitle>DECIMAL</navtitle></titlealts> + <prolog> + <metadata> + <data name="Category" value="Impala"/> + <data name="Category" value="Impala Data Types"/> + <data name="Category" value="SQL"/> + <data name="Category" value="Data Analysts"/> + <data name="Category" value="Developers"/> + <data name="Category" value="Schemas"/> + </metadata> + </prolog> + + <conbody> + + <p> + A numeric data type with fixed scale and precision, used in <codeph>CREATE TABLE</codeph> and <codeph>ALTER + TABLE</codeph> statements. Suitable for financial and other arithmetic calculations where the imprecise + representation and rounding behavior of <codeph>FLOAT</codeph> and <codeph>DOUBLE</codeph> make those types + impractical. + </p> + + <p conref="../shared/impala_common.xml#common/syntax_blurb"/> + + <p> + In the column definition of a <codeph>CREATE TABLE</codeph> statement: + </p> + +<codeblock><varname>column_name</varname> DECIMAL[(<varname>precision</varname>[,<varname>scale</varname>])]</codeblock> + + <p> + <codeph>DECIMAL</codeph> with no precision or scale values is equivalent to <codeph>DECIMAL(9,0)</codeph>. + </p> + + <p> + <b>Precision and Scale:</b> + </p> + + <p> + <varname>precision</varname> represents the total number of digits that can be represented by the column, + regardless of the location of the decimal point. This value must be between 1 and 38. For example, + representing integer values up to 9999, and floating-point values up to 99.99, both require a precision of 4. + You can also represent corresponding negative values, without any change in the precision. For example, the + range -9999 to 9999 still only requires a precision of 4. + </p> + + <p> + <varname>scale</varname> represents the number of fractional digits. This value must be less than or equal to + <varname>precision</varname>. A scale of 0 produces integral values, with no fractional part. If precision + and scale are equal, all the digits come after the decimal point, making all the values between 0 and + 0.999... or 0 and -0.999... + </p> + + <p> + When <varname>precision</varname> and <varname>scale</varname> are omitted, a <codeph>DECIMAL</codeph> value + is treated as <codeph>DECIMAL(9,0)</codeph>, that is, an integer value ranging from + <codeph>-999,999,999</codeph> to <codeph>999,999,999</codeph>. This is the largest <codeph>DECIMAL</codeph> + value that can still be represented in 4 bytes. If precision is specified but scale is omitted, Impala uses a + value of zero for the scale. + </p> + + <p> + Both <varname>precision</varname> and <varname>scale</varname> must be specified as integer literals, not any + other kind of constant expressions. + </p> + + <p> + To check the precision or scale for arbitrary values, you can call the + <xref href="impala_math_functions.xml#math_functions"><codeph>precision()</codeph> and + <codeph>scale()</codeph> built-in functions</xref>. For example, you might use these values to figure out how + many characters are required for various fields in a report, or to understand the rounding characteristics of + a formula as applied to a particular <codeph>DECIMAL</codeph> column. + </p> + + <p> + <b>Range:</b> + </p> + + <p> + The maximum precision value is 38. Thus, the largest integral value is represented by + <codeph>DECIMAL(38,0)</codeph> (999... with 9 repeated 38 times). The most precise fractional value (between + 0 and 1, or 0 and -1) is represented by <codeph>DECIMAL(38,38)</codeph>, with 38 digits to the right of the + decimal point. The value closest to 0 would be .0000...1 (37 zeros and the final 1). The value closest to 1 + would be .999... (9 repeated 38 times). + </p> + + <p> + For a given precision and scale, the range of <codeph>DECIMAL</codeph> values is the same in the positive and + negative directions. For example, <codeph>DECIMAL(4,2)</codeph> can represent from -99.99 to 99.99. This is + different from other integral numeric types where the positive and negative bounds differ slightly. + </p> + + <p> + When you use <codeph>DECIMAL</codeph> values in arithmetic expressions, the precision and scale of the result + value are determined as follows: + </p> + + <ul> + <li> + <p> + For addition and subtraction, the precision and scale are based on the maximum possible result, that is, + if all the digits of the input values were 9s and the absolute values were added together. + </p> +<!-- Seems like buggy output from this first query, so hiding the example for the time being. --> +<codeblock audience="Cloudera"><![CDATA[[localhost:21000] > select 50000.5 + 12.444, precision(50000.5 + 12.444), scale(50000.5 + 12.444); ++------------------+-----------------------------+-------------------------+ +| 50000.5 + 12.444 | precision(50000.5 + 12.444) | scale(50000.5 + 12.444) | ++------------------+-----------------------------+-------------------------+ +| 50012.944 | 9 | 3 | ++------------------+-----------------------------+-------------------------+ +[localhost:21000] > select 99999.9 + 99.999, precision(99999.9 + 99.999), scale(99999.9 + 99.999); ++------------------+-----------------------------+-------------------------+ +| 99999.9 + 99.999 | precision(99999.9 + 99.999) | scale(99999.9 + 99.999) | ++------------------+-----------------------------+-------------------------+ +| 100099.899 | 9 | 3 | ++------------------+-----------------------------+-------------------------+ +]]> +</codeblock> + </li> + + <li> + <p> + For multiplication, the precision is the sum of the precisions of the input values. The scale is the sum + of the scales of the input values. + </p> + </li> + +<!-- Need to add some specifics to discussion of division. Details here: http://blogs.msdn.com/b/sqlprogrammability/archive/2006/03/29/564110.aspx --> + + <li> + <p> + For division, Impala sets the precision and scale to values large enough to represent the whole and + fractional parts of the result. + </p> + </li> + + <li> + <p> + For <codeph>UNION</codeph>, the scale is the larger of the scales of the input values, and the precision + is increased if necessary to accommodate any additional fractional digits. If the same input value has + the largest precision and the largest scale, the result value has the same precision and scale. If one + value has a larger precision but smaller scale, the scale of the result value is increased. For example, + <codeph>DECIMAL(20,2) UNION DECIMAL(8,6)</codeph> produces a result of type + <codeph>DECIMAL(24,6)</codeph>. The extra 4 fractional digits of scale (6-2) are accommodated by + extending the precision by the same amount (20+4). + </p> + </li> + + <li> + <p> + To doublecheck, you can always call the <codeph>PRECISION()</codeph> and <codeph>SCALE()</codeph> + functions on the results of an arithmetic expression to see the relevant values, or use a <codeph>CREATE + TABLE AS SELECT</codeph> statement to define a column based on the return type of the expression. + </p> + </li> + </ul> + + <p conref="../shared/impala_common.xml#common/compatibility_blurb"/> + + <ul> + <li> + Using the <codeph>DECIMAL</codeph> type is only supported under <keyword keyref="impala14_full"/> and higher. + </li> + + <li> + Use the <codeph>DECIMAL</codeph> data type in Impala for applications where you used the + <codeph>NUMBER</codeph> data type in Oracle. The Impala <codeph>DECIMAL</codeph> type does not support the + Oracle idioms of <codeph>*</codeph> for scale or negative values for precision. + </li> + </ul> + + <p> + <b>Conversions and casting:</b> + </p> + + <p> + <ph conref="../shared/impala_common.xml#common/cast_int_to_timestamp"/> + </p> + + <p> + Impala automatically converts between <codeph>DECIMAL</codeph> and other numeric types where possible. A + <codeph>DECIMAL</codeph> with zero scale is converted to or from the smallest appropriate integral type. A + <codeph>DECIMAL</codeph> with a fractional part is automatically converted to or from the smallest + appropriate floating-point type. If the destination type does not have sufficient precision or scale to hold + all possible values of the source type, Impala raises an error and does not convert the value. + </p> + + <p> + For example, these statements show how expressions of <codeph>DECIMAL</codeph> and other types are reconciled + to the same type in the context of <codeph>UNION</codeph> queries and <codeph>INSERT</codeph> statements: + </p> + +<codeblock><![CDATA[[localhost:21000] > select cast(1 as int) as x union select cast(1.5 as decimal(9,4)) as x; ++----------------+ +| x | ++----------------+ +| 1.5000 | +| 1.0000 | ++----------------+ +[localhost:21000] > create table int_vs_decimal as select cast(1 as int) as x union select cast(1.5 as decimal(9,4)) as x; ++-------------------+ +| summary | ++-------------------+ +| Inserted 2 row(s) | ++-------------------+ +[localhost:21000] > desc int_vs_decimal; ++------+---------------+---------+ +| name | type | comment | ++------+---------------+---------+ +| x | decimal(14,4) | | ++------+---------------+---------+ +]]> +</codeblock> + + <p> + To avoid potential conversion errors, you can use <codeph>CAST()</codeph> to convert <codeph>DECIMAL</codeph> + values to <codeph>FLOAT</codeph>, <codeph>TINYINT</codeph>, <codeph>SMALLINT</codeph>, <codeph>INT</codeph>, + <codeph>BIGINT</codeph>, <codeph>STRING</codeph>, <codeph>TIMESTAMP</codeph>, or <codeph>BOOLEAN</codeph>. + You can use exponential notation in <codeph>DECIMAL</codeph> literals or when casting from + <codeph>STRING</codeph>, for example <codeph>1.0e6</codeph> to represent one million. + </p> + + <p> + If you cast a value with more fractional digits than the scale of the destination type, any extra fractional + digits are truncated (not rounded). Casting a value to a target type with not enough precision produces a + result of <codeph>NULL</codeph> and displays a runtime warning. + </p> + +<codeblock><![CDATA[[localhost:21000] > select cast(1.239 as decimal(3,2)); ++-----------------------------+ +| cast(1.239 as decimal(3,2)) | ++-----------------------------+ +| 1.23 | ++-----------------------------+ +[localhost:21000] > select cast(1234 as decimal(3)); ++----------------------------+ +| cast(1234 as decimal(3,0)) | ++----------------------------+ +| NULL | ++----------------------------+ +WARNINGS: Expression overflowed, returning NULL +]]> +</codeblock> + + <p> + When you specify integer literals, for example in <codeph>INSERT ... VALUES</codeph> statements or arithmetic + expressions, those numbers are interpreted as the smallest applicable integer type. You must use + <codeph>CAST()</codeph> calls for some combinations of integer literals and <codeph>DECIMAL</codeph> + precision. For example, <codeph>INT</codeph> has a maximum value that is 10 digits long, + <codeph>TINYINT</codeph> has a maximum value that is 3 digits long, and so on. If you specify a value such as + 123456 to go into a <codeph>DECIMAL</codeph> column, Impala checks if the column has enough precision to + represent the largest value of that integer type, and raises an error if not. Therefore, use an expression + like <codeph>CAST(123456 TO DECIMAL(9,0))</codeph> for <codeph>DECIMAL</codeph> columns with precision 9 or + less, <codeph>CAST(50 TO DECIMAL(2,0))</codeph> for <codeph>DECIMAL</codeph> columns with precision 2 or + less, and so on. For <codeph>DECIMAL</codeph> columns with precision 10 or greater, Impala automatically + interprets the value as the correct <codeph>DECIMAL</codeph> type; however, because + <codeph>DECIMAL(10)</codeph> requires 8 bytes of storage while <codeph>DECIMAL(9)</codeph> requires only 4 + bytes, only use precision of 10 or higher when actually needed. + </p> + +<codeblock><![CDATA[[localhost:21000] > create table decimals_9_0 (x decimal); +[localhost:21000] > insert into decimals_9_0 values (1), (2), (4), (8), (16), (1024), (32768), (65536), (1000000); +ERROR: AnalysisException: Possible loss of precision for target table 'decimal_testing.decimals_9_0'. +Expression '1' (type: INT) would need to be cast to DECIMAL(9,0) for column 'x' +[localhost:21000] > insert into decimals_9_0 values (cast(1 as decimal)), (cast(2 as decimal)), (cast(4 as decimal)), (cast(8 as decimal)), (cast(16 as decimal)), (cast(1024 as decimal)), (cast(32768 as decimal)), (cast(65536 as decimal)), (cast(1000000 as decimal)); + +[localhost:21000] > create table decimals_10_0 (x decimal(10,0)); +[localhost:21000] > insert into decimals_10_0 values (1), (2), (4), (8), (16), (1024), (32768), (65536), (1000000); +]]> +</codeblock> + + <p> + Be aware that in memory and for binary file formats such as Parquet or Avro, <codeph>DECIMAL(10)</codeph> or + higher consumes 8 bytes while <codeph>DECIMAL(9)</codeph> (the default for <codeph>DECIMAL</codeph>) or lower + consumes 4 bytes. Therefore, to conserve space in large tables, use the smallest-precision + <codeph>DECIMAL</codeph> type that is appropriate and <codeph>CAST()</codeph> literal values where necessary, + rather than declaring <codeph>DECIMAL</codeph> columns with high precision for convenience. + </p> + + <p> + To represent a very large or precise <codeph>DECIMAL</codeph> value as a literal, for example one that + contains more digits than can be represented by a <codeph>BIGINT</codeph> literal, use a quoted string or a + floating-point value for the number, and <codeph>CAST()</codeph> to the desired <codeph>DECIMAL</codeph> + type: + </p> + +<codeblock>insert into decimals_38_5 values (1), (2), (4), (8), (16), (1024), (32768), (65536), (1000000), + (cast("999999999999999999999999999999" as decimal(38,5))), + (cast(999999999999999999999999999999. as decimal(38,5))); +</codeblock> + + <ul> + <li> + <p> The result of the <codeph>SUM()</codeph> aggregate function on + <codeph>DECIMAL</codeph> values is promoted to a precision of 38, + with the same precision as the underlying column. Thus, the result can + represent the largest possible value at that particular precision. </p> + </li> + + <li> + <p> + <codeph>STRING</codeph> columns, literals, or expressions can be converted to <codeph>DECIMAL</codeph> as + long as the overall number of digits and digits to the right of the decimal point fit within the + specified precision and scale for the declared <codeph>DECIMAL</codeph> type. By default, a + <codeph>DECIMAL</codeph> value with no specified scale or precision can hold a maximum of 9 digits of an + integer value. If there are more digits in the string value than are allowed by the + <codeph>DECIMAL</codeph> scale and precision, the result is <codeph>NULL</codeph>. + </p> + <p> + The following examples demonstrate how <codeph>STRING</codeph> values with integer and fractional parts + are represented when converted to <codeph>DECIMAL</codeph>. If the scale is 0, the number is treated + as an integer value with a maximum of <varname>precision</varname> digits. If the precision is greater than + 0, the scale must be increased to account for the digits both to the left and right of the decimal point. + As the precision increases, output values are printed with additional trailing zeros after the decimal + point if needed. Any trailing zeros after the decimal point in the <codeph>STRING</codeph> value must fit + within the number of digits specified by the precision. + </p> +<codeblock><![CDATA[[localhost:21000] > select cast('100' as decimal); -- Small integer value fits within 9 digits of scale. ++-----------------------------+ +| cast('100' as decimal(9,0)) | ++-----------------------------+ +| 100 | ++-----------------------------+ +[localhost:21000] > select cast('100' as decimal(3,0)); -- Small integer value fits within 3 digits of scale. ++-----------------------------+ +| cast('100' as decimal(3,0)) | ++-----------------------------+ +| 100 | ++-----------------------------+ +[localhost:21000] > select cast('100' as decimal(2,0)); -- 2 digits of scale is not enough! ++-----------------------------+ +| cast('100' as decimal(2,0)) | ++-----------------------------+ +| NULL | ++-----------------------------+ +[localhost:21000] > select cast('100' as decimal(3,1)); -- (3,1) = 2 digits left of the decimal point, 1 to the right. Not enough. ++-----------------------------+ +| cast('100' as decimal(3,1)) | ++-----------------------------+ +| NULL | ++-----------------------------+ +[localhost:21000] > select cast('100' as decimal(4,1)); -- 4 digits total, 1 to the right of the decimal point. ++-----------------------------+ +| cast('100' as decimal(4,1)) | ++-----------------------------+ +| 100.0 | ++-----------------------------+ +[localhost:21000] > select cast('98.6' as decimal(3,1)); -- (3,1) can hold a 3 digit number with 1 fractional digit. ++------------------------------+ +| cast('98.6' as decimal(3,1)) | ++------------------------------+ +| 98.6 | ++------------------------------+ +[localhost:21000] > select cast('98.6' as decimal(15,1)); -- Larger scale allows bigger numbers but still only 1 fractional digit. ++-------------------------------+ +| cast('98.6' as decimal(15,1)) | ++-------------------------------+ +| 98.6 | ++-------------------------------+ +[localhost:21000] > select cast('98.6' as decimal(15,5)); -- Larger precision allows more fractional digits, outputs trailing zeros. ++-------------------------------+ +| cast('98.6' as decimal(15,5)) | ++-------------------------------+ +| 98.60000 | ++-------------------------------+ +[localhost:21000] > select cast('98.60000' as decimal(15,1)); -- Trailing zeros in the string must fit within 'scale' digits (1 in this case). ++-----------------------------------+ +| cast('98.60000' as decimal(15,1)) | ++-----------------------------------+ +| NULL | ++-----------------------------------+ +]]> +</codeblock> + </li> + + <li> + Most built-in arithmetic functions such as <codeph>SIN()</codeph> and <codeph>COS()</codeph> continue to + accept only <codeph>DOUBLE</codeph> values because they are so commonly used in scientific context for + calculations of IEEE 954-compliant values. The built-in functions that accept and return + <codeph>DECIMAL</codeph> are: +<!-- List from Skye: positive, negative, least, greatest, fnv_hash, if, nullif, zeroifnull, isnull, coalesce --> +<!-- Nong had already told me about abs, ceil, floor, round, truncate --> + <ul> + <li> + <codeph>ABS()</codeph> + </li> + + <li> + <codeph>CEIL()</codeph> + </li> + + <li> + <codeph>COALESCE()</codeph> + </li> + + <li> + <codeph>FLOOR()</codeph> + </li> + + <li> + <codeph>FNV_HASH()</codeph> + </li> + + <li> + <codeph>GREATEST()</codeph> + </li> + + <li> + <codeph>IF()</codeph> + </li> + + <li> + <codeph>ISNULL()</codeph> + </li> + + <li> + <codeph>LEAST()</codeph> + </li> + + <li> + <codeph>NEGATIVE()</codeph> + </li> + + <li> + <codeph>NULLIF()</codeph> + </li> + + <li> + <codeph>POSITIVE()</codeph> + </li> + + <li> + <codeph>PRECISION()</codeph> + </li> + + <li> + <codeph>ROUND()</codeph> + </li> + + <li> + <codeph>SCALE()</codeph> + </li> + + <li> + <codeph>TRUNCATE()</codeph> + </li> + + <li> + <codeph>ZEROIFNULL()</codeph> + </li> + </ul> + See <xref href="impala_functions.xml#builtins"/> for details. + </li> + + <li> + <p> + <codeph>BIGINT</codeph>, <codeph>INT</codeph>, <codeph>SMALLINT</codeph>, and <codeph>TINYINT</codeph> + values can all be cast to <codeph>DECIMAL</codeph>. The number of digits to the left of the decimal point + in the <codeph>DECIMAL</codeph> type must be sufficient to hold the largest value of the corresponding + integer type. Note that integer literals are treated as the smallest appropriate integer type, meaning + there is sometimes a range of values that require one more digit of <codeph>DECIMAL</codeph> scale than + you might expect. For integer values, the precision of the <codeph>DECIMAL</codeph> type can be zero; if + the precision is greater than zero, remember to increase the scale value by an equivalent amount to hold + the required number of digits to the left of the decimal point. + </p> + <p> + The following examples show how different integer types are converted to <codeph>DECIMAL</codeph>. + </p> +<!-- According to Nong, it's a bug that so many integer digits can be converted to a DECIMAL + value with small (s,p) spec. So expect to re-do this example. --> +<codeblock><![CDATA[[localhost:21000] > select cast(1 as decimal(1,0)); ++-------------------------+ +| cast(1 as decimal(1,0)) | ++-------------------------+ +| 1 | ++-------------------------+ +[localhost:21000] > select cast(9 as decimal(1,0)); ++-------------------------+ +| cast(9 as decimal(1,0)) | ++-------------------------+ +| 9 | ++-------------------------+ +[localhost:21000] > select cast(10 as decimal(1,0)); ++--------------------------+ +| cast(10 as decimal(1,0)) | ++--------------------------+ +| 10 | ++--------------------------+ +[localhost:21000] > select cast(10 as decimal(1,1)); ++--------------------------+ +| cast(10 as decimal(1,1)) | ++--------------------------+ +| 10.0 | ++--------------------------+ +[localhost:21000] > select cast(100 as decimal(1,1)); ++---------------------------+ +| cast(100 as decimal(1,1)) | ++---------------------------+ +| 100.0 | ++---------------------------+ +[localhost:21000] > select cast(1000 as decimal(1,1)); ++----------------------------+ +| cast(1000 as decimal(1,1)) | ++----------------------------+ +| 1000.0 | ++----------------------------+ +]]> +</codeblock> + </li> + + <li> + <p> + When a <codeph>DECIMAL</codeph> value is converted to any of the integer types, any fractional part is + truncated (that is, rounded towards zero): + </p> +<codeblock><![CDATA[[localhost:21000] > create table num_dec_days (x decimal(4,1)); +[localhost:21000] > insert into num_dec_days values (1), (2), (cast(4.5 as decimal(4,1))); +[localhost:21000] > insert into num_dec_days values (cast(0.1 as decimal(4,1))), (cast(.9 as decimal(4,1))), (cast(9.1 as decimal(4,1))), (cast(9.9 as decimal(4,1))); +[localhost:21000] > select cast(x as int) from num_dec_days; ++----------------+ +| cast(x as int) | ++----------------+ +| 1 | +| 2 | +| 4 | +| 0 | +| 0 | +| 9 | +| 9 | ++----------------+ +]]> +</codeblock> + </li> + + <li> + <p> + You cannot directly cast <codeph>TIMESTAMP</codeph> or <codeph>BOOLEAN</codeph> values to or from + <codeph>DECIMAL</codeph> values. You can turn a <codeph>DECIMAL</codeph> value into a time-related + representation using a two-step process, by converting it to an integer value and then using that result + in a call to a date and time function such as <codeph>from_unixtime()</codeph>. + </p> +<codeblock><![CDATA[[localhost:21000] > select from_unixtime(cast(cast(1000.0 as decimal) as bigint)); ++-------------------------------------------------------------+ +| from_unixtime(cast(cast(1000.0 as decimal(9,0)) as bigint)) | ++-------------------------------------------------------------+ +| 1970-01-01 00:16:40 | ++-------------------------------------------------------------+ +[localhost:21000] > select now() + interval cast(x as int) days from num_dec_days; -- x is a DECIMAL column. + +[localhost:21000] > create table num_dec_days (x decimal(4,1)); +[localhost:21000] > insert into num_dec_days values (1), (2), (cast(4.5 as decimal(4,1))); +[localhost:21000] > select now() + interval cast(x as int) days from num_dec_days; -- The 4.5 value is truncated to 4 and becomes '4 days'. ++--------------------------------------+ +| now() + interval cast(x as int) days | ++--------------------------------------+ +| 2014-05-13 23:11:55.163284000 | +| 2014-05-14 23:11:55.163284000 | +| 2014-05-16 23:11:55.163284000 | ++--------------------------------------+ +]]> +</codeblock> + </li> + + <li> + <p> + Because values in <codeph>INSERT</codeph> statements are checked rigorously for type compatibility, be + prepared to use <codeph>CAST()</codeph> function calls around literals, column references, or other + expressions that you are inserting into a <codeph>DECIMAL</codeph> column. + </p> + </li> + </ul> + + <p conref="../shared/impala_common.xml#common/null_bad_numeric_cast"/> + + <p> + <b>DECIMAL differences from integer and floating-point types:</b> + </p> + + <p> + With the <codeph>DECIMAL</codeph> type, you are concerned with the number of overall digits of a number + rather than powers of 2 (as in <codeph>TINYINT</codeph>, <codeph>SMALLINT</codeph>, and so on). Therefore, + the limits with integral values of <codeph>DECIMAL</codeph> types fall around 99, 999, 9999, and so on rather + than 32767, 65535, 2 + <sup>32</sup> + -1, and so on. For fractional values, you do not need to account for imprecise representation of the + fractional part according to the IEEE-954 standard (as in <codeph>FLOAT</codeph> and + <codeph>DOUBLE</codeph>). Therefore, when you insert a fractional value into a <codeph>DECIMAL</codeph> + column, you can compare, sum, query, <codeph>GROUP BY</codeph>, and so on that column and get back the + original values rather than some <q>close but not identical</q> value. + </p> + + <p> + <codeph>FLOAT</codeph> and <codeph>DOUBLE</codeph> can cause problems or unexpected behavior due to inability + to precisely represent certain fractional values, for example dollar and cents values for currency. You might + find output values slightly different than you inserted, equality tests that do not match precisely, or + unexpected values for <codeph>GROUP BY</codeph> columns. <codeph>DECIMAL</codeph> can help reduce unexpected + behavior and rounding errors, at the expense of some performance overhead for assignments and comparisons. + </p> + + <p> + <b>Literals and expressions:</b> + <ul> + <li> + <p> + When you use an integer literal such as <codeph>1</codeph> or <codeph>999</codeph> in a SQL statement, + depending on the context, Impala will treat it as either the smallest appropriate + <codeph>DECIMAL</codeph> type, or the smallest integer type (<codeph>TINYINT</codeph>, + <codeph>SMALLINT</codeph>, <codeph>INT</codeph>, or <codeph>BIGINT</codeph>). To minimize memory usage, + Impala prefers to treat the literal as the smallest appropriate integer type. + </p> + </li> + + <li> + <p> + When you use a floating-point literal such as <codeph>1.1</codeph> or <codeph>999.44</codeph> in a SQL + statement, depending on the context, Impala will treat it as either the smallest appropriate + <codeph>DECIMAL</codeph> type, or the smallest floating-point type (<codeph>FLOAT</codeph> or + <codeph>DOUBLE</codeph>). To avoid loss of accuracy, Impala prefers to treat the literal as a + <codeph>DECIMAL</codeph>. + </p> + </li> + </ul> + </p> + + <p> + <b>Storage considerations:</b> + </p> + + <ul> + <li> + Only the precision determines the storage size for <codeph>DECIMAL</codeph> values; the scale setting has + no effect on the storage size. + </li> + + <li> + Text, RCFile, and SequenceFile tables all use ASCII-based formats. In these text-based file formats, + leading zeros are not stored, but trailing zeros are stored. In these tables, each <codeph>DECIMAL</codeph> + value takes up as many bytes as there are digits in the value, plus an extra byte if the decimal point is + present and an extra byte for negative values. Once the values are loaded into memory, they are represented + in 4, 8, or 16 bytes as described in the following list items. The on-disk representation varies depending + on the file format of the table. + </li> + +<!-- Next couple of points can be conref'ed with identical list bullets farther down under File Format Considerations. --> + + <li> + Parquet and Avro tables use binary formats, In these tables, Impala stores each value in as few bytes as + possible +<!-- 4, 8, or 16 bytes --> + depending on the precision specified for the <codeph>DECIMAL</codeph> column. + <ul> + <li> + In memory, <codeph>DECIMAL</codeph> values with precision of 9 or less are stored in 4 bytes. + </li> + + <li> + In memory, <codeph>DECIMAL</codeph> values with precision of 10 through 18 are stored in 8 bytes. + </li> + + <li> + In memory, <codeph>DECIMAL</codeph> values with precision greater than 18 are stored in 16 bytes. + </li> + </ul> + </li> + </ul> + + <p conref="../shared/impala_common.xml#common/file_format_blurb"/> + + <ul> + <li> + The <codeph>DECIMAL</codeph> data type can be stored in any of the file formats supported by Impala, as + described in <xref href="impala_file_formats.xml#file_formats"/>. Impala only writes to tables that use the + Parquet and text formats, so those formats are the focus for file format compatibility. + </li> + + <li> + Impala can query Avro, RCFile, or SequenceFile tables containing <codeph>DECIMAL</codeph> columns, created + by other Hadoop components, on CDH 5 only. + </li> + + <li> + You can use <codeph>DECIMAL</codeph> columns in Impala tables that are mapped to HBase tables. Impala can + query and insert into such tables. + </li> + + <li> + Text, RCFile, and SequenceFile tables all use ASCII-based formats. In these tables, each + <codeph>DECIMAL</codeph> value takes up as many bytes as there are digits in the value, plus an extra byte + if the decimal point is present. The binary format of Parquet or Avro files offers more compact storage for + <codeph>DECIMAL</codeph> columns. + </li> + + <li> + Parquet and Avro tables use binary formats, In these tables, Impala stores each value in 4, 8, or 16 bytes + depending on the precision specified for the <codeph>DECIMAL</codeph> column. + </li> + + <li> + Parquet files containing <codeph>DECIMAL</codeph> columns are not expected to be readable under CDH 4. See + the <b>Compatibility</b> section for details. + </li> + </ul> + + <p> + <b>UDF considerations:</b> When writing a C++ UDF, use the <codeph>DecimalVal</codeph> data type defined in + <filepath>/usr/include/impala_udf/udf.h</filepath>. + </p> + + <p conref="../shared/impala_common.xml#common/partitioning_blurb"/> + + <p> + You can use a <codeph>DECIMAL</codeph> column as a partition key. Doing so provides a better match between + the partition key values and the HDFS directory names than using a <codeph>DOUBLE</codeph> or + <codeph>FLOAT</codeph> partitioning column: + </p> + + <p conref="../shared/impala_common.xml#common/schema_evolution_blurb"/> + + <ul> + <li> + For text-based formats (text, RCFile, and SequenceFile tables), you can issue an <codeph>ALTER TABLE ... + REPLACE COLUMNS</codeph> statement to change the precision and scale of an existing + <codeph>DECIMAL</codeph> column. As long as the values in the column fit within the new precision and + scale, they are returned correctly by a query. Any values that do not fit within the new precision and + scale are returned as <codeph>NULL</codeph>, and Impala reports the conversion error. Leading zeros do not + count against the precision value, but trailing zeros after the decimal point do. +<codeblock><![CDATA[[localhost:21000] > create table text_decimals (x string); +[localhost:21000] > insert into text_decimals values ("1"), ("2"), ("99.99"), ("1.234"), ("000001"), ("1.000000000"); +[localhost:21000] > select * from text_decimals; ++-------------+ +| x | ++-------------+ +| 1 | +| 2 | +| 99.99 | +| 1.234 | +| 000001 | +| 1.000000000 | ++-------------+ +[localhost:21000] > alter table text_decimals replace columns (x decimal(4,2)); +[localhost:21000] > select * from text_decimals; ++-------+ +| x | ++-------+ +| 1.00 | +| 2.00 | +| 99.99 | +| NULL | +| 1.00 | +| NULL | ++-------+ +ERRORS: +Backend 0:Error converting column: 0 TO DECIMAL(4, 2) (Data is: 1.234) +file: hdfs://127.0.0.1:8020/user/hive/warehouse/decimal_testing.db/text_decimals/634d4bd3aa0 +e8420-b4b13bab7f1be787_56794587_data.0 +record: 1.234 +Error converting column: 0 TO DECIMAL(4, 2) (Data is: 1.000000000) +file: hdfs://127.0.0.1:8020/user/hive/warehouse/decimal_testing.db/text_decimals/cd40dc68e20 +c565a-cc4bd86c724c96ba_311873428_data.0 +record: 1.000000000 +]]> +</codeblock> + </li> + + <li> + For binary formats (Parquet and Avro tables), although an <codeph>ALTER TABLE ... REPLACE COLUMNS</codeph> + statement that changes the precision or scale of a <codeph>DECIMAL</codeph> column succeeds, any subsequent + attempt to query the changed column results in a fatal error. (The other columns can still be queried + successfully.) This is because the metadata about the columns is stored in the data files themselves, and + <codeph>ALTER TABLE</codeph> does not actually make any updates to the data files. If the metadata in the + data files disagrees with the metadata in the metastore database, Impala cancels the query. + </li> + </ul> + + <p conref="../shared/impala_common.xml#common/example_blurb"/> + +<codeblock>CREATE TABLE t1 (x DECIMAL, y DECIMAL(5,2), z DECIMAL(25,0)); +INSERT INTO t1 VALUES (5, 99.44, 123456), (300, 6.7, 999999999); +SELECT x+y, ROUND(y,1), z/98.6 FROM t1; +SELECT CAST(1000.5 AS DECIMAL); +</codeblock> + + <p conref="../shared/impala_common.xml#common/restrictions_blurb"/> + + <p conref="../shared/impala_common.xml#common/decimal_no_stats"/> + +<!-- <p conref="../shared/impala_common.xml#common/partitioning_good"/> --> + + <p conref="../shared/impala_common.xml#common/hbase_ok"/> + + <p conref="../shared/impala_common.xml#common/parquet_ok"/> + + <p conref="../shared/impala_common.xml#common/text_bulky"/> + +<!-- <p conref="../shared/impala_common.xml#common/compatibility_blurb"/> --> + +<!-- <p conref="../shared/impala_common.xml#common/internals_blurb"/> --> + +<!-- <p conref="../shared/impala_common.xml#common/added_in_20"/> --> + + <p conref="../shared/impala_common.xml#common/column_stats_constant"/> + + <p conref="../shared/impala_common.xml#common/related_info"/> + + <p> + <xref href="impala_literals.xml#numeric_literals"/>, <xref href="impala_tinyint.xml#tinyint"/>, + <xref href="impala_smallint.xml#smallint"/>, <xref href="impala_int.xml#int"/>, + <xref href="impala_bigint.xml#bigint"/>, <xref href="impala_decimal.xml#decimal"/>, + <xref href="impala_math_functions.xml#math_functions"/> (especially <codeph>PRECISION()</codeph> and + <codeph>SCALE()</codeph>) + </p> + </conbody> +</concept> http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/3be0f122/docs/topics/impala_default_order_by_limit.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_default_order_by_limit.xml b/docs/topics/impala_default_order_by_limit.xml new file mode 100644 index 0000000..94f6899 --- /dev/null +++ b/docs/topics/impala_default_order_by_limit.xml @@ -0,0 +1,37 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> +<concept rev="obwl" id="default_order_by_limit"> + + <title>DEFAULT_ORDER_BY_LIMIT Query Option</title> + <titlealts audience="PDF"><navtitle>DEFAULT_ORDER_BY_LIMIT</navtitle></titlealts> + <prolog> + <metadata> + <data name="Category" value="Impala"/> + <data name="Category" value="Impala Query Options"/> + <data name="Category" value="Developers"/> + <data name="Category" value="Data Analysts"/> + </metadata> + </prolog> + + <conbody> + + <p conref="../shared/impala_common.xml#common/obwl_query_options"/> + + <p rev="1.4.0"> + Prior to Impala 1.4.0, Impala queries that use the <codeph><xref href="impala_order_by.xml#order_by">ORDER + BY</xref></codeph> clause must also include a + <codeph><xref href="impala_limit.xml#limit">LIMIT</xref></codeph> clause, to avoid accidentally producing + huge result sets that must be sorted. Sorting a huge result set is a memory-intensive operation. In Impala + 1.4.0 and higher, Impala uses a temporary disk work area to perform the sort if that operation would + otherwise exceed the Impala memory limit on a particular host. + </p> + + <p> + <b>Type: numeric</b> + </p> + + <p> + <b>Default:</b> -1 (no default limit) + </p> + </conbody> +</concept> http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/3be0f122/docs/topics/impala_delegation.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_delegation.xml b/docs/topics/impala_delegation.xml new file mode 100644 index 0000000..0d59761 --- /dev/null +++ b/docs/topics/impala_delegation.xml @@ -0,0 +1,88 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> +<concept rev="1.2" id="delegation"> + + <title>Configuring Impala Delegation for Hue and BI Tools</title> + + <prolog> + <metadata> + <data name="Category" value="Security"/> + <data name="Category" value="Impala"/> + <data name="Category" value="Authentication"/> + <data name="Category" value="Delegation"/> + <data name="Category" value="Hue"/> + <data name="Category" value="Administrators"/> + <data name="Category" value="Developers"/> + <data name="Category" value="Data Analysts"/> + </metadata> + </prolog> + + <conbody> + + <p> +<!-- + When users connect to Impala directly through the <cmdname>impala-shell</cmdname> interpreter, the Sentry + authorization framework determines what actions they can take and what data they can see. +--> + When users submit Impala queries through a separate application, such as Hue or a business intelligence tool, + typically all requests are treated as coming from the same user. In Impala 1.2 and higher, authentication is + extended by a new feature that allows applications to pass along credentials for the users that connect to + them (known as <q>delegation</q>), and issue Impala queries with the privileges for those users. Currently, + the delegation feature is available only for Impala queries submitted through application interfaces such as + Hue and BI tools; for example, Impala cannot issue queries using the privileges of the HDFS user. + </p> + + <p> + The delegation feature is enabled by a startup option for <cmdname>impalad</cmdname>: + <codeph>--authorized_proxy_user_config</codeph>. When you specify this option, users whose names you specify + (such as <codeph>hue</codeph>) can delegate the execution of a query to another user. The query runs with the + privileges of the delegated user, not the original user such as <codeph>hue</codeph>. The name of the + delegated user is passed using the HiveServer2 configuration property <codeph>impala.doas.user</codeph>. + </p> + + <p> + You can specify a list of users that the application user can delegate to, or <codeph>*</codeph> to allow a + superuser to delegate to any other user. For example: + </p> + +<codeblock>impalad --authorized_proxy_user_config 'hue=user1,user2;admin=*' ...</codeblock> + + <note> + Make sure to use single quotes or escape characters to ensure that any <codeph>*</codeph> characters do not + undergo wildcard expansion when specified in command-line arguments. + </note> + + <p> + See <xref href="impala_config_options.xml#config_options"/> for details about adding or changing + <cmdname>impalad</cmdname> startup options. See + <xref href="http://blog.cloudera.com/blog/2013/07/how-hiveserver2-brings-security-and-concurrency-to-apache-hive/"; scope="external" format="html">this + Cloudera blog post</xref> for background information about the delegation capability in HiveServer2. + </p> + + <p> + To set up authentication for the delegated users: + </p> + + <ul> + <li> + <p> + On the server side, configure either user/password authentication through LDAP, or Kerberos + authentication, for all the delegated users. See <xref href="impala_ldap.xml#ldap"/> or + <xref href="impala_kerberos.xml#kerberos"/> for details. + </p> + </li> + + <li> + <p> + On the client side, follow the instructions in the <q>Using User Name and Password</q> section in the + <xref href="http://www.cloudera.com/content/cloudera-content/cloudera-docs/Connectors/PDF/Cloudera-ODBC-Driver-for-Impala-Install-Guide.pdf"; scope="external" format="pdf">ODBC + driver installation guide</xref>. Then search for <q>delegation</q> in that same installation guide to + learn about the <uicontrol>Delegation UID</uicontrol> field and <codeph>DelegationUID</codeph> configuration keyword to enable the delegation feature for + ODBC-based BI tools. + </p> + </li> + </ul> + + </conbody> + +</concept> http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/3be0f122/docs/topics/impala_delete.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_delete.xml b/docs/topics/impala_delete.xml new file mode 100644 index 0000000..5715cc7 --- /dev/null +++ b/docs/topics/impala_delete.xml @@ -0,0 +1,65 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> +<concept id="delete"> + + <title>DELETE Statement (<keyword keyref="impala28"/> or higher only)</title> + <titlealts audience="PDF"><navtitle>DELETE</navtitle></titlealts> + <prolog> + <metadata> + <data name="Category" value="Impala"/> + <data name="Category" value="SQL"/> + <data name="Category" value="Kudu"/> + <data name="Category" value="ETL"/> + <data name="Category" value="Ingest"/> + <data name="Category" value="DML"/> + <data name="Category" value="Developers"/> + <data name="Category" value="Data Analysts"/> + </metadata> + </prolog> + + <conbody> + + <p> + <indexterm audience="Cloudera">DELETE statement</indexterm> + Deletes one or more rows from a Kudu table. + Although deleting a single row or a range of rows would be inefficient for tables using HDFS + data files, Kudu is able to perform this operation efficiently. Therefore, this statement + only works for Impala tables that use the Kudu storage engine. + </p> + + <p conref="../shared/impala_common.xml#common/syntax_blurb"/> + +<codeblock> +</codeblock> + + <p rev="kudu"> + Normally, a <codeph>DELETE</codeph> operation for a Kudu table fails if + some partition key columns are not found, due to their being deleted or changed + by a concurrent <codeph>UPDATE</codeph> or <codeph>DELETE</codeph> operation. + Specify <codeph>DELETE IGNORE <varname>rest_of_statement</varname></codeph> to + make the <codeph>DELETE</codeph> continue in this case. The rows with the nonexistent + duplicate partition key column values are not removed. + </p> + + <p conref="../shared/impala_common.xml#common/dml_blurb"/> + + <p conref="../shared/impala_common.xml#common/usage_notes_blurb"/> + + <p conref="../shared/impala_common.xml#common/sync_ddl_blurb"/> + + <note conref="../shared/impala_common.xml#common/compute_stats_next"/> + + <p conref="../shared/impala_common.xml#common/example_blurb"/> +<codeblock> + +</codeblock> + + <p conref="../shared/impala_common.xml#common/related_info"/> + + <p> + <xref href="impala_kudu.xml#impala_kudu"/> + </p> + + </conbody> + +</concept>
