v3: preserve trailing comments

[sougou]

@enisoc
Trailing comments are often used as additional annotation
for queries, especially DML. To support this, Vitess preserves
trailing comments. V3 was not doing this. This change fixes
the behavior.

Implementation: The trailing comments have to be first removed
to allow for the query to match the plan cache. The comments
are then re-added just before routing. This is done for every
query.

Vindex operations are considered to be internal. So, the comments
are not propagated into those.

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This change is

[enisoc]

Previously, sougou wrote…

v3: preserve trailing comments

@enisoc

Trailing comments are often used as additional annotation

for queries, especially DML. To support this, Vitess preserves

trailing comments. V3 was not doing this. This change fixes

the behavior.

Implementation: The trailing comments have to be first removed

to allow for the query to match the plan cache. The comments

are then re-added just before routing. This is done for every

query.

Vindex operations are considered to be internal. So, the comments

are not propagated into those.

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Reviewed 10 of 10 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved, some commit checks failed.

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Comments from Reviewable