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sql/opt: add locking durability
In addition to strength and wait policy, we now add a third property to locks: durability. Locks with `LockDurabilityGuaranteed` are guaranteed to be held until commit (if the transaction commits). Durable locks must be used when correctness depends on locking. This is never the case under our `SERIALIZABLE` isolation, but under `SNAPSHOT` and `READ COMMITTED` isolation it will be the case for `SELECT FOR UPDATE` statements, which will be the first users of durable locks. This commit adds locking durability to the optimizer and `EXPLAIN` output, but does not plumb it into KV yet. It will be used in the next commit to temporarily disallow `SELECT FOR UPDATE` statements under `SNAPSHOT` and `READ COMMITTED` isolation. Release note: None
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9 files changed

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‎pkg/sql/catalog/descpb/locking.proto‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -115,7 +115,7 @@ enum ScanLockingStrength {
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// on each key scanned.
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FOR_UPDATE = 4;
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}
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// LockingWaitPolicy controls the policy used for handling conflicting locks
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// held by other active transactions when attempting to lock rows due to FOR
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// UPDATE/SHARE clauses (i.e. it represents the NOWAIT and SKIP LOCKED options).

‎pkg/sql/opt/exec/execbuilder/mutation.go‎

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -973,8 +973,12 @@ func (b *Builder) canAutoCommit(rel memo.RelExpr) bool {
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// forUpdateLocking is the row-level locking mode used by mutations during their
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// initial row scan, when such locking is deemed desirable. The locking mode is
976-
// equivalent that used by a SELECT ... FOR UPDATE statement.
977-
var forUpdateLocking = opt.Locking{Strength: tree.ForUpdate}
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// equivalent to that used by a SELECT FOR UPDATE statement, except not durable.
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var forUpdateLocking = opt.Locking{
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Strength: tree.ForUpdate,
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WaitPolicy: tree.LockWaitBlock,
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Durability: tree.LockDurabilityBestEffort,
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}
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// shouldApplyImplicitLockingToMutationInput determines whether or not the
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// builder should apply a FOR UPDATE row-level locking mode to the initial row

‎pkg/sql/opt/exec/execbuilder/relational.go‎

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -620,7 +620,7 @@ func (b *Builder) scanParams(
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locking := scan.Locking
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if b.forceForUpdateLocking {
623-
locking = forUpdateLocking
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locking = locking.Max(forUpdateLocking)
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}
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b.ContainsNonDefaultKeyLocking = b.ContainsNonDefaultKeyLocking || locking.IsLocking()
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@@ -2172,7 +2172,7 @@ func (b *Builder) buildIndexJoin(join *memo.IndexJoinExpr) (execPlan, error) {
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locking := join.Locking
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if b.forceForUpdateLocking {
2175-
locking = forUpdateLocking
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locking = locking.Max(forUpdateLocking)
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}
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b.ContainsNonDefaultKeyLocking = b.ContainsNonDefaultKeyLocking || locking.IsLocking()
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@@ -2493,7 +2493,7 @@ func (b *Builder) buildLookupJoin(join *memo.LookupJoinExpr) (execPlan, error) {
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locking := join.Locking
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if b.forceForUpdateLocking {
2496-
locking = forUpdateLocking
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locking = locking.Max(forUpdateLocking)
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}
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b.ContainsNonDefaultKeyLocking = b.ContainsNonDefaultKeyLocking || locking.IsLocking()
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@@ -2735,7 +2735,7 @@ func (b *Builder) buildInvertedJoin(join *memo.InvertedJoinExpr) (execPlan, erro
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locking := join.Locking
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if b.forceForUpdateLocking {
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locking = forUpdateLocking
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locking = locking.Max(forUpdateLocking)
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}
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b.ContainsNonDefaultKeyLocking = b.ContainsNonDefaultKeyLocking || locking.IsLocking()
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@@ -2816,8 +2816,8 @@ func (b *Builder) buildZigzagJoin(join *memo.ZigzagJoinExpr) (execPlan, error) {
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leftLocking := join.LeftLocking
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rightLocking := join.RightLocking
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if b.forceForUpdateLocking {
2819-
leftLocking = forUpdateLocking
2820-
rightLocking = forUpdateLocking
2819+
leftLocking = leftLocking.Max(forUpdateLocking)
2820+
rightLocking = rightLocking.Max(forUpdateLocking)
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}
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b.ContainsNonDefaultKeyLocking = b.ContainsNonDefaultKeyLocking || leftLocking.IsLocking() || rightLocking.IsLocking()
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