sql: pool some of the processor allocations

[yuzefovich]

execinfra: fix temporary memory leak of expressions

This commit fixes the way we reuse the ProcOutputHelpers. Previously, we
would not perform the deep reset of the render expressions which could
lead to those expressions being live for longer than needed (namely till
the helper is reused the next time). This matters when the ProcessorBase
is reused which currently only happens when TableReaders are used from
the sync.Pool. This probably was a pretty bad issue before the
vectorized engine, but nowadays its impact seems minor. Still, it's good
to fix it, especially given the following commit which will introduce
more pooling of processors.

Release note: None

execinfra: reuse output row allocation in the helper

This commit makes it so that we reuse the output row in the
ProcOutputHelper if possible. Additionally, it removes a row alloc
object since it is not helpful and only leeds to wasteful allocations.
It also removes a redundant integer for the number of "internal
columns".

Release note: None

[cockroach-teamcity]

This change is 

[yuzefovich]

First commit is #88831 and should be ignored here.

[DrewKimball]

Nice work!

Reviewed 10 of 10 files at r5, 1 of 1 files at r6, 2 of 2 files at r7.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @DrewKimball, @michae2, and @yuzefovich)

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pkg/sql/colexec/columnarizer.go line 168 at r8 (raw file):

		execinfra.ProcStateOpts{
			// We append input to inputs to drain below in order to reuse the same
			// underlying slice from the pooled noopProcessor.

[nit] noopProcessor -> columnarizer

[yuzefovich]

TFTR!

bors r+

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @DrewKimball and @michae2)

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pkg/sql/colexec/columnarizer.go line 168 at r8 (raw file):

Previously, DrewKimball (Drew Kimball) wrote…

[nit] noopProcessor -> columnarizer

Done.

[craig]

Build failed (retrying...):

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[craig]

Build failed (retrying...):

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[craig]

Build failed (retrying...):

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[craig]

Build failed:

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[yuzefovich]

bors r+

[craig]

Build failed:

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[yuzefovich]

bors r+

[craig]

Build failed:

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[yuzefovich]

Alright, these bors failures were legitimate, need to make some tweaks.

[yuzefovich]

I'm still working through some things, so please hold off on reviewing - I'll ping once it's ready for a look.

[yuzefovich]

It's not as easy of a fix, so I removed the last commit that exposed a pre-existing bug (will file an issue soon) and will merge just the first two simple commits.

bors r+

[craig]

Build succeeded:

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