VStream: Skip vindex keyrange filtering when we can

[mattlord]

Description

We were always adding in_keyrange filters for a vstream when the target keyspace was sharded. This PR adds a check to see if the shard mappings are 1:1 and the key ranges are equal for both shards — if so then we do not add the in_keyrange filter.

When that filter is in place, every row/binlog event on the VReplication stream source must have its KeyspaceID calculated before adding it to the vstream for the target. This same filter from the VReplication record is also used when a VDiff is performed for the workflow. In the case of VDiff, this means that each source tablet needs to calculate the KeyspaceID for every record read from its mysqld before adding it to the vstream used for the diff.

This additional vindex work can be costly — in particular during the VDiff where you are reading every row from each table that you're diffing in quick succession — and especially so for more complex vindex types such as unicode_loose_md5, so skipping that work whenever possible is a good optimization.

That is what this PR does.

Related Issue(s)

• Fixes: Feature Request: Optimize in_keyrange filtering for VReplication workflows #14388

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

[vitess-bot]

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[dbussink]

This is a very useful optimization and we'll also look at optimizing this when we do need to call this as well.