GitHub user gatorsmile opened a pull request:
https://github.com/apache/spark/pull/11148
[Spark-13263] [SQL] SQL Generation Support for Tablesample
In the parser, tableSample clause is part of tableSource.
```
tableSource
@init { gParent.pushMsg("table source", state); }
@after { gParent.popMsg(state); }
: tabname=tableName
((tableProperties) => props=tableProperties)?
((tableSample) => ts=tableSample)?
((KW_AS) => (KW_AS alias=Identifier)
|
(Identifier) => (alias=Identifier))?
-> ^(TOK_TABREF $tabname $props? $ts? $alias?)
;
```
Two typical query samples using TABLESAMPLE are:
```
"SELECT s.id FROM t0 TABLESAMPLE(10 PERCENT) s"
"SELECT * FROM t0 TABLESAMPLE(0.1 PERCENT)"
```
FYI, the logical plan of a TABLESAMPLE query:
```
sql("SELECT * FROM t0 TABLESAMPLE(0.1 PERCENT)").explain(true)
== Analyzed Logical Plan ==
id: bigint
Project [id#16L]
+- Sample 0.0, 0.001, false, 381
+- Subquery t0
+- Relation[id#16L] ParquetRelation
```
Thanks! cc @liancheng
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gatorsmile/spark tablesplitsample
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/11148.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #11148
----
commit 58b60383486eaa174ca7c579c3f0f75e1f3d58d0
Author: gatorsmile <[email protected]>
Date: 2016-02-10T06:44:15Z
support tablesample
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