storage: allow multiple iterators in pebbleReadOnly and pebbleBatch#81195
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craig[bot] merged 1 commit intocockroachdb:masterfrom May 16, 2022
Merged
storage: allow multiple iterators in pebbleReadOnly and pebbleBatch#81195craig[bot] merged 1 commit intocockroachdb:masterfrom
pebbleReadOnly and pebbleBatch#81195craig[bot] merged 1 commit intocockroachdb:masterfrom
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Previously, `pebbleReadOnly` and `pebbleBatch` only supported a single concurrent iterator of a given type, as this iterator was reused between `NewMVCCIterator` calls. Attempts to create an additional iterator would panic with "iterator already in use". Time-bound iterators were excluded from this reuse, and always created from scratch, so they sidestepped this limitation. However, we will soon make these iterators reusable too via a new `SetOptions()` method in Pebble. When TBIs also become reusable, this will cause `MVCCIncrementalIterator` to panic with "iterator already in use", because it always creates two concurrent iterators: one regular and one time-bound. This patch therefore ensures all `Reader` implementations support multiple concurrent iterators, by cloning the existing cached iterator if it is already in use. This also preserves the pinned engine state for the new iterator. Release note: None
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This was referenced May 13, 2022
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Reviewed 3 of 3 files at r1, all commit messages.
Reviewable status:complete! 1 of 0 LGTMs obtained (waiting on @aliher1911, @nicktrav, and @sumeerbhola)
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TFTR! bors r=jbowens |
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Partial resubmit of #79291, which was merged into the mvcc-range-tombstones branch.
Previously,
pebbleReadOnlyandpebbleBatchonly supported a singleconcurrent iterator of a given type, as this iterator was reused between
NewMVCCIteratorcalls. Attempts to create an additional iterator wouldpanic with "iterator already in use".
Time-bound iterators were excluded from this reuse, and always created
from scratch, so they sidestepped this limitation. However, we will soon
make these iterators reusable too via a new
SetOptions()method inPebble. When TBIs also become reusable, this will cause
MVCCIncrementalIteratorto panic with "iterator already in use",because it always creates two concurrent iterators: one regular and one
time-bound.
This patch therefore ensures all
Readerimplementations supportmultiple concurrent iterators, by cloning the existing cached iterator
if it is already in use. This also preserves the pinned engine state for
the new iterator.
Release note: None