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sql: parser and optimizer support FOR {UPDATE,SHARE} SKIP LOCKED #85720

Merged
merged 2 commits into from
Aug 10, 2022
Merged

sql: parser and optimizer support FOR {UPDATE,SHARE} SKIP LOCKED #85720

merged 2 commits into from
Aug 10, 2022

Commits on Aug 9, 2022

  1. sql: enable the skip-locked wait policy 

    Now that KV support this, we can pass the wait policy through.

Fixes cockroachdb#40476

Release note (sql change): SELECT ... FOR {UPDATE,SHARE} SKIP LOCKED
is now supported. The option can be used to skip rows that cannot be
immediately locked instead of blocking on contended row-level lock
acquisition.
    @nvanbenschoten @rytaft
    nvanbenschoten authored and rytaft committed Aug 9, 2022
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  2. opt: optimizer updates for support of SKIP LOCKED 

    For queries using SELECT FOR {SHARE,UPDATE} SKIP LOCKED, we need to disable
optimizations that depend on preserved-multiplicity consistency of
tables. When SKIP LOCKED is used, we will no longer use optimizations that
assume:
- a PK row exists for every secondary index row
- a PK row exists for every referencing FK (if the PK table uses SKIP LOCKED)

One result of this change is that we will no longer push limits into index
joins if the primary index uses locking wait policy SKIP LOCKED.

This commit also disallows use of multiple column families in tables scanned
with SKIP LOCKED, since it could result in returning partial rows.

Release note: None

Co-authored-by: Michael Erickson <[email protected]>
    @rytaft @michae2
    rytaft and michae2 committed Aug 9, 2022
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