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Unnest simple subqueries #6831

Merged
merged 2 commits into from
Oct 11, 2020
Merged

Unnest simple subqueries #6831

merged 2 commits into from
Oct 11, 2020

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systay
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@systay systay commented Oct 7, 2020 •
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This PR adds logic to simplify subquery expressions that are simple to unnest.

If a query contains an expression looking something like:

SELECT * FROM user WHERE col = (SELECT 42)

this PR will unnest that subquery so that the query that is planned is instead:

SELECT * FROM user WHERE col = 42

Fixes #6827

harshit-gangal
harshit-gangal approved these changes Oct 7, 2020
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go/test/endtoend/vtgate/misc_test.go Outdated
Comment on lines 381 to 383
exec(t, conn, "SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = (SELECT SCHEMA()) AND TABLE_NAME = 'product' AND COLUMN_KEY = 'PRI'")
}
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nice to add assert for the query result.

GuptaManan100
GuptaManan100 approved these changes Oct 8, 2020
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LGTM

harshit-gangal
harshit-gangal requested changes Oct 8, 2020
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As I approved this earlier, making this as blocking so that I understand the change before merging.

go/vt/vtgate/executor_select_test.go Outdated Show resolved Hide resolved
harshit-gangal
harshit-gangal approved these changes Oct 8, 2020
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I looked as old commit. Ignore my previous comment.
One comment on test expectations.

go/vt/vtgate/executor_select_test.go Outdated Show resolved Hide resolved
@systay systay changed the title Rewrite more queries Unnest simple subqueries Oct 8, 2020
@systay systay added the Type: Enhancement Logical improvement (somewhere between a bug and feature) label Oct 8, 2020
@systay
refactor expression rewriting
139f048 
Signed-off-by: Andres Taylor <andres@planetscale.com>
@systay
Unnest subqueries that don't need to be subqueries
c1d81af 
Signed-off-by: Andres Taylor <andres@planetscale.com>
@systay systay merged commit c8114b4 into vitessio:master Oct 11, 2020
@askdba askdba modified the milestone: v8.0 Oct 12, 2020
@rafael rafael mentioned this pull request Mar 17, 2021
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@harshit-gangal harshit-gangal harshit-gangal approved these changes

@GuptaManan100 GuptaManan100 GuptaManan100 approved these changes

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Component: Query Serving Type: Enhancement Logical improvement (somewhere between a bug and feature)
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INFORMATION_SCHEMA.TABLE_SCHEMA comparison with dynamic value no longer works
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@systay @harshit-gangal @GuptaManan100 @askdba