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[SPARK-13321][SQL] Support nested UNION in parser #11204

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[SPARK-13321][SQL] Support nested UNION in parser #11204

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93bd51e
Support nested UNION in parser.
viirya Feb 15, 2016
f462997
Test actual parsed plan.
viirya Feb 15, 2016
190b326
Support recursively nested one.
viirya Feb 15, 2016
a00261d
Merge remote-tracking branch 'upstream/master' into nested-union
viirya Feb 21, 2016
d024fff
Merge remote-tracking branch 'upstream/master' into nested-union
viirya Feb 21, 2016
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20 changes: 20 additions & 0 deletions sql/catalyst/src/main/antlr3/org/apache/spark/sql/catalyst/parser/SparkSqlParser.g
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Original file line number Diff line number Diff line change
Expand Up @@ -2320,6 +2320,26 @@ regularBody[boolean topLevel]
)
|
selectStatement[topLevel]
|
(LPAREN selectStatement0[true]) => nestedSetOpSelectStatement[topLevel]
;

nestedSetOpSelectStatement[boolean topLevel]
:
(
LPAREN s=selectStatement0[topLevel] RPAREN -> {$s.tree}
)
(set=setOpSelectStatement[$nestedSetOpSelectStatement.tree, topLevel])
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@hvanhovell hvanhovell Feb 15, 2016

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Discussion: This works but is quite had to follow (passing the matched tree to the next rule). Isn't there a more simple & concise approach possible?

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@viirya viirya Feb 15, 2016

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I've tried few approaches unsuccessfully. I will try if there is more simple approach tomorrow.

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@viirya viirya Feb 16, 2016

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I made a little change to support recursively nested UNION. I also updated the test. But it is basically the same approach.

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@viirya viirya Feb 16, 2016

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I think it might be the simplest approach to support recursively nested UNION query.

-> {set == null}?
{$nestedSetOpSelectStatement.tree}
-> {$set.tree}
;

selectStatement0[boolean topLevel]
:
(selectStatement[true]) => selectStatement[topLevel]
|
(nestedSetOpSelectStatement[true]) => nestedSetOpSelectStatement[topLevel]
;

selectStatement[boolean topLevel]
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64 changes: 64 additions & 0 deletions sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/CatalystQlSuite.scala
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Expand Up @@ -203,6 +203,70 @@ class CatalystQlSuite extends PlanTest {
"from windowData")
}

test("nesting UNION") {
val parsed = parser.parsePlan(
"""
|SELECT `u_1`.`id` FROM (((SELECT `t0`.`id` FROM `default`.`t0`)
|UNION ALL (SELECT `t0`.`id` FROM `default`.`t0`)) UNION ALL
|(SELECT `t0`.`id` FROM `default`.`t0`)) AS u_1
""".stripMargin)

val expected = Project(
UnresolvedAlias(UnresolvedAttribute("u_1.id"), None) :: Nil,
Subquery("u_1",
Union(
Union(
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None)),
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None))),
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None)))))

comparePlans(parsed, expected)

val parsedSame = parser.parsePlan(
"""
|SELECT `u_1`.`id` FROM ((SELECT `t0`.`id` FROM `default`.`t0`)
|UNION ALL (SELECT `t0`.`id` FROM `default`.`t0`) UNION ALL
|(SELECT `t0`.`id` FROM `default`.`t0`)) AS u_1
""".stripMargin)

comparePlans(parsedSame, expected)

val parsed2 = parser.parsePlan(
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@viirya viirya Feb 16, 2016

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Recursively nested UNION.

"""
|SELECT `u_1`.`id` FROM ((((SELECT `t0`.`id` FROM `default`.`t0`)
|UNION ALL (SELECT `t0`.`id` FROM `default`.`t0`)) UNION ALL
|(SELECT `t0`.`id` FROM `default`.`t0`))
|UNION ALL (SELECT `t0`.`id` FROM `default`.`t0`)) AS u_1
""".stripMargin)

val expected2 = Project(
UnresolvedAlias(UnresolvedAttribute("u_1.id"), None) :: Nil,
Subquery("u_1",
Union(
Union(
Union(
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None)),
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None))),
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None))),
Project(
UnresolvedAlias(UnresolvedAttribute("t0.id"), None) :: Nil,
UnresolvedRelation(TableIdentifier("t0", Some("default")), None)))))

comparePlans(parsed2, expected2)
}

test("subquery") {
parser.parsePlan("select (select max(b) from s) ss from t")
parser.parsePlan("select * from t where a = (select b from s)")
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