[SPARK-50449][SQL] Fix SQL Scripting grammar allowing empty bodies for loops, IF and CASE#48989
[SPARK-50449][SQL] Fix SQL Scripting grammar allowing empty bodies for loops, IF and CASE#48989dusantism-db wants to merge 5 commits intoapache:masterfrom
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Does it also make sense to add test with for with empty body, in this PR or your other one, depending on which you merge first?
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Yes, I will add it to the one which gets merged last, or if they both get merged then I will create a separate PR.
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Added tests for FOR
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Can we also add test like the one in PR description:
WHILE 1=1 DO
BEGIN
END;
END WHILE;
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I will add that one in the follow up PR, as that case is still not fixed.
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@dusantism-db Could you open an JIRA and prepend it to PR's title, please.
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@MaxGekk done |
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Why are the changes needed?
The existing grammar was wrong.
Why is it wrong? Can you provide a few words from either SQL standard, specs or other references.
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@srielau PTAL |
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I thought we should throw exception in the getOrElse branch, how does this fix work?
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If ctx.compoundBody() is null, that means we have
BEGIN
END;
This is allowed, so in this case we simply return a CompoundBody with empty statements list.
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LGTM.
We want to allow empty BEGIN END
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thanks, merging to master! |
This PR depends on #48989 ### What changes were proposed in this pull request? There is a bug in SQL scripting which causes empty compound statements to throw an error if their body consists solely of empty BEGIN END blocks. Examples: ``` WHILE 1 = 1 DO BEGIN END; END WHILE; ``` ``` BEGIN BEGIN BEGIN END; END; END; ``` This PR fixes this by introducing a NO-OP statement for SQL scripting, which empty BEGIN END blocks will return. ### Why are the changes needed? Currenty, compound bodies declare they have the next element even if their body is consisted only of empty blocks. This is because it only checks for existence of statements in the body, not whether there is at least one statement which is not an empty block. ### Does this PR introduce _any_ user-facing change? No. ### How was this patch tested? Unit tests were added to existing suites. ### Was this patch authored or co-authored using generative AI tooling? No. Closes #49064 from dusantism-db/scripting-noop-statement. Authored-by: Dušan Tišma <dusan.tisma@databricks.com> Signed-off-by: Wenchen Fan <wenchen@databricks.com>
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What changes were proposed in this pull request?
Before this PR, SQL Scripting grammar allowed for loops, IF and CASE to have empty bodies. Example:
WHILE 1 = 1 DO END WHILE;If they have an empty body, an internal error is thrown during execution. This PR changes the grammar so that loops, IF and CASE must have at least one statement in their bodies.
Note that this does not completely fix the internal error issue. It is still possible to have something like
where the same error is still thrown, except this construct is correct grammar wise.
This issue will be fixed by a separate PR, as non-trivial interpreter logic changes are required.
Why are the changes needed?
The existing grammar was wrong.
Does this PR introduce any user-facing change?
No.
How was this patch tested?
Unit tests that make sure parsing loops, IF and CASE with empty bodies throws an error.
Was this patch authored or co-authored using generative AI tooling?
No.