Repository: impala Updated Branches: refs/heads/master 2b4d06710 -> 34fd9732e
IMPALA-7395: [DOCS] The TABLE keyword is optional in the TRUNCATE statement Change-Id: Iec64cd225449cea07b353201a84ac2fb8bc07a00 Reviewed-on: http://gerrit.cloudera.org:8080/11120 Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com> Reviewed-by: Tim Armstrong <tarmstr...@cloudera.com> Project: http://git-wip-us.apache.org/repos/asf/impala/repo Commit: http://git-wip-us.apache.org/repos/asf/impala/commit/2aa9ca25 Tree: http://git-wip-us.apache.org/repos/asf/impala/tree/2aa9ca25 Diff: http://git-wip-us.apache.org/repos/asf/impala/diff/2aa9ca25 Branch: refs/heads/master Commit: 2aa9ca25f4e33537cd1da3d373804866d5335262 Parents: 2b4d067 Author: Alex Rodoni <arod...@cloudera.com> Authored: Fri Aug 3 16:13:19 2018 -0700 Committer: Alex Rodoni <arod...@cloudera.com> Committed: Fri Aug 3 23:35:07 2018 +0000 ---------------------------------------------------------------------- docs/topics/impala_truncate_table.xml | 133 +++++++++++------------------ 1 file changed, 51 insertions(+), 82 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/impala/blob/2aa9ca25/docs/topics/impala_truncate_table.xml ---------------------------------------------------------------------- diff --git a/docs/topics/impala_truncate_table.xml b/docs/topics/impala_truncate_table.xml index cf0e0a4..e40802c 100644 --- a/docs/topics/impala_truncate_table.xml +++ b/docs/topics/impala_truncate_table.xml @@ -35,85 +35,58 @@ under the License. </prolog> <conbody> - <p rev="2.3.0"> - <indexterm audience="hidden">TRUNCATE TABLE statement</indexterm> - Removes the data from an Impala table while leaving the table itself. - </p> - + <indexterm audience="hidden">TRUNCATE TABLE statement</indexterm> Removes + the data from an Impala table while leaving the table itself. </p> <p conref="../shared/impala_common.xml#common/syntax_blurb"/> - -<codeblock>TRUNCATE TABLE <ph rev="2.5.0 IMPALA-2641">[IF EXISTS]</ph> [<varname>db_name</varname>.]<varname>table_name</varname></codeblock> - + <codeblock>TRUNCATE [TABLE] <ph rev="2.5.0 IMPALA-2641">[IF EXISTS]</ph> [<varname>db_name</varname>.]<varname>table_name</varname></codeblock> <p conref="../shared/impala_common.xml#common/ddl_blurb"/> - <p conref="../shared/impala_common.xml#common/usage_notes_blurb"/> - - <p> - Often used to empty tables that are used during ETL cycles, after the data has been copied to another - table for the next stage of processing. This statement is a low-overhead alternative to dropping and - recreating the table, or using <codeph>INSERT OVERWRITE</codeph> to replace the data during the - next ETL cycle. - </p> - - <p> - This statement removes all the data and associated data files in the table. It can remove data files from internal tables, - external tables, partitioned tables, and tables mapped to HBase or the Amazon Simple Storage Service (S3). - The data removal applies to the entire table, including all partitions of a partitioned table. - </p> - - <p> - Any statistics produced by the <codeph>COMPUTE STATS</codeph> statement are reset when the data is removed. - </p> - - <p> - Make sure that you are in the correct database before truncating a table, either by issuing a - <codeph>USE</codeph> statement first or by using a fully qualified name - <codeph><varname>db_name</varname>.<varname>table_name</varname></codeph>. - </p> - - <p rev="2.5.0 IMPALA-2641"> - The optional <codeph>IF EXISTS</codeph> clause makes the statement succeed whether or not the table exists. - If the table does exist, it is truncated; if it does not exist, the statement has no effect. This capability is - useful in standardized setup scripts that are might be run both before and after some of the tables exist. - This clause is available in <keyword keyref="impala25_full"/> and higher. - </p> - - <p> - Any HDFS data files removed by this statement go into the HDFS trashcan, from which you can recover them - within a defined time interval if this operation turns out to be a mistake. - </p> - + <p> Often used to empty tables that are used during ETL cycles, after the + data has been copied to another table for the next stage of processing. + This statement is a low-overhead alternative to dropping and recreating + the table, or using <codeph>INSERT OVERWRITE</codeph> to replace the data + during the next ETL cycle. </p> + <p> This statement removes all the data and associated data files in the + table. It can remove data files from internal tables, external tables, + partitioned tables, and tables mapped to HBase or the Amazon Simple + Storage Service (S3). The data removal applies to the entire table, + including all partitions of a partitioned table. </p> + <p> Any statistics produced by the <codeph>COMPUTE STATS</codeph> statement + are reset when the data is removed. </p> + <p> Make sure that you are in the correct database before truncating a + table, either by issuing a <codeph>USE</codeph> statement first or by + using a fully qualified name + <codeph><varname>db_name</varname>.<varname>table_name</varname></codeph>. </p> + <p>The optional <codeph>TABLE</codeph> keyword does not affect the behavior + of the statement.</p> + <p rev="2.5.0 IMPALA-2641"> The optional <codeph>IF EXISTS</codeph> clause + makes the statement succeed whether or not the table exists. If the table + does exist, it is truncated; if it does not exist, the statement has no + effect. This capability is useful in standardized setup scripts that are + might be run both before and after some of the tables exist. This clause + is available in <keyword keyref="impala25_full"/> and higher. </p> + <p> Any HDFS data files removed by this statement go into the HDFS trashcan, + from which you can recover them within a defined time interval if this + operation turns out to be a mistake. </p> <p conref="../shared/impala_common.xml#common/disk_space_blurb"/> - <p conref="../shared/impala_common.xml#common/s3_blurb"/> - <p rev="2.2.0"> - Although Impala cannot write new data to a table stored in the Amazon - S3 filesystem, the <codeph>TRUNCATE TABLE</codeph> statement can remove data files from S3. - See <xref href="impala_s3.xml#s3"/> for details about working with S3 tables. - </p> - + <p rev="2.2.0"> Although Impala cannot write new data to a table stored in + the Amazon S3 filesystem, the <codeph>TRUNCATE TABLE</codeph> statement + can remove data files from S3. See <xref href="impala_s3.xml#s3"/> for + details about working with S3 tables. </p> <p conref="../shared/impala_common.xml#common/cancel_blurb_no"/> - <p conref="../shared/impala_common.xml#common/permissions_blurb"/> - <p rev=""> - The user ID that the <cmdname>impalad</cmdname> daemon runs under, - typically the <codeph>impala</codeph> user, must have write - permission for all the files and directories that make up the table. - </p> - + <p rev=""> The user ID that the <cmdname>impalad</cmdname> daemon runs + under, typically the <codeph>impala</codeph> user, must have write + permission for all the files and directories that make up the table. </p> <p conref="../shared/impala_common.xml#common/kudu_blurb"/> <p conref="../shared/impala_common.xml#common/kudu_no_truncate_table"/> - <p conref="../shared/impala_common.xml#common/example_blurb"/> - - <p> - The following example shows a table containing some data and with table and column statistics. - After the <codeph>TRUNCATE TABLE</codeph> statement, the data is removed and the statistics - are reset. - </p> - -<codeblock>CREATE TABLE truncate_demo (x INT); + <p> The following example shows a table containing some data and with table + and column statistics. After the <codeph>TRUNCATE TABLE</codeph> + statement, the data is removed and the statistics are reset. </p> + <codeblock>CREATE TABLE truncate_demo (x INT); INSERT INTO truncate_demo VALUES (1), (2), (4), (8); SELECT COUNT(*) FROM truncate_demo; +----------+ @@ -162,13 +135,10 @@ SHOW COLUMN STATS truncate_demo; | x | INT | -1 | -1 | 4 | 4 | +--------+------+------------------+--------+----------+----------+ </codeblock> - - <p> - The following example shows how the <codeph>IF EXISTS</codeph> clause allows the <codeph>TRUNCATE TABLE</codeph> - statement to be run without error whether or not the table exists: - </p> - -<codeblock rev="2.5.0 IMPALA-2641">CREATE TABLE staging_table1 (x INT, s STRING); + <p> The following example shows how the <codeph>IF EXISTS</codeph> clause + allows the <codeph>TRUNCATE TABLE</codeph> statement to be run without + error whether or not the table exists: </p> + <codeblock rev="2.5.0 IMPALA-2641">CREATE TABLE staging_table1 (x INT, s STRING); Fetched 0 row(s) in 0.33s SHOW TABLES LIKE 'staging*'; @@ -191,15 +161,14 @@ Fetched 0 row(s) in 0.25s TRUNCATE TABLE IF EXISTS staging_table3; Fetched 0 row(s) in 0.25s </codeblock> - <p conref="../shared/impala_common.xml#common/related_info"/> - <p> - <xref href="impala_tables.xml#tables"/>, - <xref href="impala_alter_table.xml#alter_table"/>, <xref href="impala_create_table.xml#create_table"/>, - <xref href="impala_partitioning.xml#partitioning"/>, <xref href="impala_tables.xml#internal_tables"/>, - <xref href="impala_tables.xml#external_tables"/> + <xref href="impala_tables.xml#tables"/>, <xref + href="impala_alter_table.xml#alter_table"/>, <xref + href="impala_create_table.xml#create_table"/>, <xref + href="impala_partitioning.xml#partitioning"/>, <xref + href="impala_tables.xml#internal_tables"/>, <xref + href="impala_tables.xml#external_tables"/> </p> - </conbody> </concept>
