sql: enable the skip-locked wait policy

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

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.

pkg/sql/catalog/descpb/locking.proto

@@ -124,9 +124,6 @@ enum ScanLockingWaitPolicy {
   BLOCK = 0;
 
   // SKIP_LOCKED represents SKIP LOCKED - skip rows that can't be locked.
-  //
-  // NOTE: SKIP_LOCKED is not currently implemented and does not make it out of
-  // the SQL optimizer without throwing an error.
   SKIP_LOCKED = 1;
 
   // ERROR represents NOWAIT - raise an error if a row cannot be locked.

pkg/sql/logictest/testdata/logic_test/select_for_update

@@ -53,31 +53,38 @@ SELECT 1 FOR UPDATE OF public.a
 query error pgcode 42601 FOR UPDATE must specify unqualified relation names
 SELECT 1 FOR UPDATE OF db.public.a
 
-# We don't currently support SKIP LOCKED, since it returns an inconsistent view
-# and generally has strange semantics with respect to serializable isolation.
-# Support may be added in the future.
-
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 SELECT 1 FOR UPDATE SKIP LOCKED
+----
+1
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 SELECT 1 FOR NO KEY UPDATE SKIP LOCKED
+----
+1
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 SELECT 1 FOR SHARE SKIP LOCKED
+----
+1
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 SELECT 1 FOR KEY SHARE SKIP LOCKED
+----
+1
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query error pgcode 42P01 relation "a" in FOR UPDATE clause not found in FROM clause
 SELECT 1 FOR UPDATE OF a SKIP LOCKED
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query error pgcode 42P01 relation "a" in FOR UPDATE clause not found in FROM clause
 SELECT 1 FOR UPDATE OF a SKIP LOCKED FOR NO KEY UPDATE OF b SKIP LOCKED
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query error pgcode 42P01 relation "a" in FOR UPDATE clause not found in FROM clause
 SELECT 1 FOR UPDATE OF a SKIP LOCKED FOR NO KEY UPDATE OF b NOWAIT
 
+query error pgcode 42P01 relation "a" in FOR UPDATE clause not found in FROM clause
+SELECT 1 FOR UPDATE OF a SKIP LOCKED FOR SHARE OF b, c SKIP LOCKED FOR NO KEY UPDATE OF d SKIP LOCKED FOR KEY SHARE OF e, f SKIP LOCKED
+
 query I
 SELECT 1 FOR UPDATE NOWAIT
 ----
@@ -105,18 +112,24 @@ query error pgcode 42P01 relation "a" in FOR UPDATE clause not found in FROM cla
 SELECT 1 FOR UPDATE OF a NOWAIT FOR NO KEY UPDATE OF b NOWAIT
 
 query error pgcode 42P01 relation "a" in FOR UPDATE clause not found in FROM clause
-SELECT 1 FOR UPDATE OF a NOWAIT FOR SHARE OF b, c NOWAIT FOR NO KEY UPDATE OF d NOWAIT  FOR KEY SHARE OF e, f NOWAIT 
+SELECT 1 FOR UPDATE OF a NOWAIT FOR SHARE OF b, c NOWAIT FOR NO KEY UPDATE OF d NOWAIT FOR KEY SHARE OF e, f NOWAIT
 
 # Locking clauses both inside and outside of parenthesis are handled correctly.
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 ((SELECT 1)) FOR UPDATE SKIP LOCKED
+----
+1
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 ((SELECT 1) FOR UPDATE SKIP LOCKED)
+----
+1
 
-query error unimplemented: SKIP LOCKED lock wait policy is not supported
+query I
 ((SELECT 1 FOR UPDATE SKIP LOCKED))
+----
+1
 
 # FOR READ ONLY is ignored, like in Postgres.
 query I
@@ -295,7 +308,7 @@ SELECT * FROM t FOR KEY SHARE
 statement ok
 ROLLBACK
 
-# The NOWAIT wait policy returns error when conflicting lock is encountered.
+# The NOWAIT wait policy returns error when a conflicting lock is encountered.
 
 statement ok
 INSERT INTO t VALUES (1, 1)
@@ -372,3 +385,50 @@ user root
 
 statement ok
 ROLLBACK
+
+# The SKIP LOCKED wait policy skip rows when a conflicting lock is encountered.
+
+statement ok
+INSERT INTO t VALUES (2, 2), (3, 3), (4, 4)
+
+statement ok
+BEGIN; UPDATE t SET v = 3 WHERE k = 2
+
+user testuser
+
+statement ok
+BEGIN
+
+query II
+SELECT * FROM t FOR UPDATE SKIP LOCKED
+----
+1  1
+3  3
+4  4
+
+statement ok
+UPDATE t SET v = 4 WHERE k = 3
+
+query II
+SELECT * FROM t FOR UPDATE SKIP LOCKED
+----
+1  1
+3  4
+4  4
+
+user root
+
+query II
+SELECT * FROM t FOR UPDATE SKIP LOCKED
+----
+2  3
+
+statement ok
+ROLLBACK
+
+user testuser
+
+statement ok
+ROLLBACK
+
+user root