storage: ignore {exclusive,shared} locks in ScanConflictingIntentsForDroppingLatchesEarly

[arulajmani]

ScanConflictingIntentsForDroppingLatchesEarly is called by non-locking read requests to check for conflicts before evaluating. Non-locking reads do not conflict with Exclusive or Shared locks -- so these can be ignored when scanning the lock table. This patch does so, by making use of an appropriately configured LockTableIterator.

Informs #100193

Release note: None

[cockroach-teamcity]

This change is 

[nvanbenschoten]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @arulajmani and @bananabrick)

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pkg/storage/engine.go line 2035 at r1 (raw file):

			return true /* needsIntentHistory */, nil
		}
		v, err := iter.UnsafeValue()

nit: iter.ValueProto avoids one of these error checks, if you want it.

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pkg/storage/engine_test.go line 2226 at r1 (raw file):

				err = MVCCAcquireLock(ctx, rw, txnA, lock.Exclusive, keyB, nil /*ms*/, 0 /*maxConflicts*/)
				require.NoError(t, err)
				require.NoError(t, err)

nit: remove this line.

[arulajmani]

Thanks!

bors r=nvanbenschoten

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @aayushshah15, @bananabrick, and @nvanbenschoten)

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pkg/storage/engine.go line 2035 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

nit: iter.ValueProto avoids one of these error checks, if you want it.

cc: @aayushshah15

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pkg/storage/engine_test.go line 2226 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

nit: remove this line.

done.

[craig]

Build failed (retrying...):

• Bazel Essential CI (Cockroach)

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)