Commits on Nov 23, 2024

1. sql: disable gossip-based physical planning by default …

   Now that we improved handling of draining procedure in the virtual
   clusters in 24.3 timeframe, I believe it's time to begin fully
   deprecating the gossip-based physical planning, and as the first step
   this commit introduces a cluster setting to control which method is used
   in single-tenant deployments (instance-based planning being the
   default). I plan to have the setting as an escape hatch in case we find
   problems when rolling out this change and to remove the setting
   altogether after 25.2.
   
   One of the differences between two planning methods is slightly adjusted
   in this commit. In particular, in the instance-based planning we stitch
   together consecutive spans whenever `EnsureSafeSplitKey` for the keys in
   the spans returns the same prefix. The idea is that spans corresponding
   to different column families of the same SQL row must be placed on the
   same instance. However, the condition on the length of the keys returned
   by `EnsureSafeSplitKey` is too broad and captures more cases than
   needed (i.e. two keys that cannot be part of the same SQL row end up in
   the same `SpanPartition`). To partially alleviate this difference, this
   commit introduces "boundary granularity" knob which indicates whether
   consecutive spans _might_ be part of the same SQL row, and we now use
   the stitching logic only if so. All callers of `PartitionSpans` have
   been audited, and we need the stitching logic only in two call sites that
   correspond to planning of table readers. Longer term, if we change the
   encoding so that column family IDs are encoded in a special way, we'll
   be able to tell definitively whether stitching is needed simply based on
   the key itself, and this additional logic could be removed.
   
   Epic: None
   
   Release note: None

   

   yuzefovich committed Nov 23, 2024
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