diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 231dc6a..fd2b7a8 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -1283,7 +1283,7 @@ FETCH { FIRST | NEXT } [ count ] {
The locking clause has the general form
-FOR lock_strength [ OF table_name [, ...] ] [ NOWAIT ]
+FOR lock_strength [ OF table_name [, ...] ] [ { NOWAIT | SKIP LOCKED DATA } ]
where lock_strength can be one of
@@ -1359,9 +1359,9 @@ KEY SHARE
To prevent the operation from waiting for other transactions to commit,
- use the NOWAIT option. With NOWAIT, the statement
+ use either the NOWAIT or SKIP LOCKED DATA option. With NOWAIT, the statement
reports an error, rather than waiting, if a selected row
- cannot be locked immediately. Note that NOWAIT applies only
+ cannot be locked immediately. With SKIP LOCKED DATA, any selected rows that cannot be immediately locked are skipped. Skipping locked rows provides an inconsistent view of the data, so this is not suitable for general purpose work, but can be used to avoid lock contention with multiple consumers accessing a queue-like table. Note that NOWAIT and SKIP LOCKED DATA apply only
to the row-level lock(s) — the required ROW SHARE
table-level lock is still taken in the ordinary way (see
). You can use
@@ -1393,7 +1393,8 @@ KEY SHARE
then it is processed as if it was only specified by the strongest one.
Similarly, a table is processed
as NOWAIT if that is specified in any of the clauses
- affecting it.
+ affecting it. Otherwise, it is processed as SKIP LOCKED
+ DATA if that is specified in any of the clauses affecting it.
@@ -1931,7 +1932,8 @@ SELECT distributors.* WHERE distributors.name = 'Westward';
query as well as in sub-SELECTs, but this is an extension.
The FOR NO KEY UPDATE, FOR SHARE and
FOR KEY SHARE variants,
- as well as the NOWAIT option,
+ as well as the NOWAIT and SKIP LOCKED DATA
+ options,
do not appear in the standard.
diff --git a/doc/src/sgml/sql.sgml b/doc/src/sgml/sql.sgml
index ba92607..b3978ff 100644
--- a/doc/src/sgml/sql.sgml
+++ b/doc/src/sgml/sql.sgml
@@ -863,7 +863,7 @@ SELECT [ ALL | DISTINCT [ ON ( expressionexpression [ ASC | DESC | USING operator ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { count | ALL } ]
[ OFFSET start ]
- [ FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NOWAIT ] [...] ]
+ [ FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ { NOWAIT | SKIP LOCKED DATA } ] [...] ]
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index a047632..458fbc7 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -4083,7 +4083,7 @@ get_mxact_status_for_lock(LockTupleMode mode, bool is_update)
* cid: current command ID (used for visibility test, and stored into
* tuple's cmax if lock is successful)
* mode: indicates if shared or exclusive tuple lock is desired
- * nowait: if true, ereport rather than blocking if lock not available
+ * wait_policy: whether to block, ereport or skip if lock not available
* follow_updates: if true, follow the update chain to also lock descendant
* tuples.
*
@@ -4096,6 +4096,7 @@ get_mxact_status_for_lock(LockTupleMode mode, bool is_update)
* HeapTupleMayBeUpdated: lock was successfully acquired
* HeapTupleSelfUpdated: lock failed because tuple updated by self
* HeapTupleUpdated: lock failed because tuple updated by other xact
+ * HeapTupleWouldBlock: lock couldn't be acquired and wait_policy is skip
*
* In the failure cases, the routine fills *hufd with the tuple's t_ctid,
* t_xmax (resolving a possible MultiXact, if necessary), and t_cmax
@@ -4107,7 +4108,7 @@ get_mxact_status_for_lock(LockTupleMode mode, bool is_update)
*/
HTSU_Result
heap_lock_tuple(Relation relation, HeapTuple tuple,
- CommandId cid, LockTupleMode mode, bool nowait,
+ CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
bool follow_updates,
Buffer *buffer, HeapUpdateFailureData *hufd)
{
@@ -4210,7 +4211,11 @@ l3:
*/
if (!have_tuple_lock)
{
- if (nowait)
+ if (wait_policy == LockWaitBlock)
+ {
+ LockTupleTuplock(relation, tid, mode);
+ }
+ else if (wait_policy == LockWaitError)
{
if (!ConditionalLockTupleTuplock(relation, tid, mode))
ereport(ERROR,
@@ -4218,8 +4223,12 @@ l3:
errmsg("could not obtain lock on row in relation \"%s\"",
RelationGetRelationName(relation))));
}
- else
- LockTupleTuplock(relation, tid, mode);
+ else /* wait_policy == LockWaitSkip */
+ {
+ if (!ConditionalLockTupleTuplock(relation, tid, mode))
+ /* TODO -- work out what needs to be released here */
+ return HeapTupleWouldBlock;
+ }
have_tuple_lock = true;
}
@@ -4421,7 +4430,7 @@ l3:
elog(ERROR, "invalid lock mode in heap_lock_tuple");
/* wait for multixact to end */
- if (nowait)
+ if (wait_policy == LockWaitError)
{
if (!ConditionalMultiXactIdWait((MultiXactId) xwait,
status, infomask, relation,
@@ -4432,10 +4441,21 @@ l3:
errmsg("could not obtain lock on row in relation \"%s\"",
RelationGetRelationName(relation))));
}
- else
+ else if (wait_policy == LockWaitBlock)
+ {
MultiXactIdWait((MultiXactId) xwait, status, infomask,
relation, &tuple->t_data->t_ctid,
XLTW_Lock, NULL);
+ }
+ else /* wait_policy == LockWaitSkip */
+ {
+ if (!ConditionalMultiXactIdWait((MultiXactId) xwait,
+ status, infomask,
+ relation, &tuple->t_data->t_ctid,
+ XLTW_Lock, NULL))
+ /* TODO -- work out what needs to be released here */
+ return HeapTupleWouldBlock;
+ }
/* if there are updates, follow the update chain */
if (follow_updates &&
@@ -4481,7 +4501,7 @@ l3:
else
{
/* wait for regular transaction to end */
- if (nowait)
+ if (wait_policy == LockWaitError)
{
if (!ConditionalXactLockTableWait(xwait))
ereport(ERROR,
@@ -4489,9 +4509,17 @@ l3:
errmsg("could not obtain lock on row in relation \"%s\"",
RelationGetRelationName(relation))));
}
- else
+ else if (wait_policy == LockWaitBlock)
+ {
XactLockTableWait(xwait, relation, &tuple->t_data->t_ctid,
XLTW_Lock);
+ }
+ else /* wait_policy == LockWaitSkip */
+ {
+ if (!ConditionalXactLockTableWait(xwait))
+ /* TODO -- work out what needs to be released here */
+ return HeapTupleWouldBlock;
+ }
/* if there are updates, follow the update chain */
if (follow_updates &&
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 5f1ccf0..4c1767e 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -2706,7 +2706,7 @@ ltrmark:;
tuple.t_self = *tid;
test = heap_lock_tuple(relation, &tuple,
estate->es_output_cid,
- lockmode, false /* wait */ ,
+ lockmode, LockWaitBlock,
false, &buffer, &hufd);
switch (test)
{
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 886c751..9cee27d 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -831,6 +831,7 @@ InitPlan(QueryDesc *queryDesc, int eflags)
erm->rowmarkId = rc->rowmarkId;
erm->markType = rc->markType;
erm->noWait = rc->noWait;
+ erm->skipLocked = rc->skipLocked;
ItemPointerSetInvalid(&(erm->curCtid));
estate->es_rowMarks = lappend(estate->es_rowMarks, erm);
}
@@ -2011,7 +2012,7 @@ EvalPlanQualFetch(EState *estate, Relation relation, int lockmode,
*/
test = heap_lock_tuple(relation, &tuple,
estate->es_output_cid,
- lockmode, false /* wait */ ,
+ lockmode, LockWaitBlock,
false, &buffer, &hufd);
/* We now have two pins on the buffer, get rid of one */
ReleaseBuffer(buffer);
diff --git a/src/backend/executor/nodeLockRows.c b/src/backend/executor/nodeLockRows.c
index ae10796..ac423a1 100644
--- a/src/backend/executor/nodeLockRows.c
+++ b/src/backend/executor/nodeLockRows.c
@@ -73,6 +73,7 @@ lnext:
Buffer buffer;
HeapUpdateFailureData hufd;
LockTupleMode lockmode;
+ LockWaitPolicy wait_policy;
HTSU_Result test;
HeapTuple copyTuple;
@@ -131,13 +132,24 @@ lnext:
break;
}
+ if (erm->noWait)
+ wait_policy = LockWaitError;
+ else if (erm->skipLocked)
+ wait_policy = LockWaitSkip;
+ else
+ wait_policy = LockWaitBlock;
+
test = heap_lock_tuple(erm->relation, &tuple,
estate->es_output_cid,
- lockmode, erm->noWait, true,
+ lockmode, wait_policy, true,
&buffer, &hufd);
ReleaseBuffer(buffer);
switch (test)
{
+ case HeapTupleWouldBlock:
+ /* couldn't lock tuple in SKIP LOCKED DATA mode */
+ goto lnext;
+
case HeapTupleSelfUpdated:
/*
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 98ad910..33dc65a 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -960,6 +960,7 @@ _copyPlanRowMark(const PlanRowMark *from)
COPY_SCALAR_FIELD(rowmarkId);
COPY_SCALAR_FIELD(markType);
COPY_SCALAR_FIELD(noWait);
+ COPY_SCALAR_FIELD(skipLocked);
COPY_SCALAR_FIELD(isParent);
return newnode;
@@ -2071,6 +2072,7 @@ _copyRowMarkClause(const RowMarkClause *from)
COPY_SCALAR_FIELD(rti);
COPY_SCALAR_FIELD(strength);
COPY_SCALAR_FIELD(noWait);
+ COPY_SCALAR_FIELD(skipLocked);
COPY_SCALAR_FIELD(pushedDown);
return newnode;
@@ -2440,6 +2442,7 @@ _copyLockingClause(const LockingClause *from)
COPY_NODE_FIELD(lockedRels);
COPY_SCALAR_FIELD(strength);
COPY_SCALAR_FIELD(noWait);
+ COPY_SCALAR_FIELD(skipLocked);
return newnode;
}
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 9901d23..5f53445 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2263,6 +2263,7 @@ _equalLockingClause(const LockingClause *a, const LockingClause *b)
COMPARE_NODE_FIELD(lockedRels);
COMPARE_SCALAR_FIELD(strength);
COMPARE_SCALAR_FIELD(noWait);
+ COMPARE_SCALAR_FIELD(skipLocked);
return true;
}
@@ -2359,6 +2360,7 @@ _equalRowMarkClause(const RowMarkClause *a, const RowMarkClause *b)
COMPARE_SCALAR_FIELD(rti);
COMPARE_SCALAR_FIELD(strength);
COMPARE_SCALAR_FIELD(noWait);
+ COMPARE_SCALAR_FIELD(skipLocked);
COMPARE_SCALAR_FIELD(pushedDown);
return true;
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 10e8139..2f8336b 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -837,6 +837,7 @@ _outPlanRowMark(StringInfo str, const PlanRowMark *node)
WRITE_UINT_FIELD(rowmarkId);
WRITE_ENUM_FIELD(markType, RowMarkType);
WRITE_BOOL_FIELD(noWait);
+ WRITE_BOOL_FIELD(skipLocked);
WRITE_BOOL_FIELD(isParent);
}
@@ -2122,6 +2123,7 @@ _outLockingClause(StringInfo str, const LockingClause *node)
WRITE_NODE_FIELD(lockedRels);
WRITE_ENUM_FIELD(strength, LockClauseStrength);
WRITE_BOOL_FIELD(noWait);
+ WRITE_BOOL_FIELD(skipLocked);
}
static void
@@ -2312,6 +2314,7 @@ _outRowMarkClause(StringInfo str, const RowMarkClause *node)
WRITE_UINT_FIELD(rti);
WRITE_ENUM_FIELD(strength, LockClauseStrength);
WRITE_BOOL_FIELD(noWait);
+ WRITE_BOOL_FIELD(skipLocked);
WRITE_BOOL_FIELD(pushedDown);
}
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index ef1eae9..a8365c8 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -321,6 +321,7 @@ _readRowMarkClause(void)
READ_UINT_FIELD(rti);
READ_ENUM_FIELD(strength, LockClauseStrength);
READ_BOOL_FIELD(noWait);
+ READ_BOOL_FIELD(skipLocked);
READ_BOOL_FIELD(pushedDown);
READ_DONE();
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 0508d16..108a792 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2228,6 +2228,7 @@ preprocess_rowmarks(PlannerInfo *root)
break;
}
newrc->noWait = rc->noWait;
+ newrc->skipLocked = rc->skipLocked;
newrc->isParent = false;
prowmarks = lappend(prowmarks, newrc);
@@ -2256,6 +2257,7 @@ preprocess_rowmarks(PlannerInfo *root)
else
newrc->markType = ROW_MARK_COPY;
newrc->noWait = false; /* doesn't matter */
+ newrc->skipLocked = false;
newrc->isParent = false;
prowmarks = lappend(prowmarks, newrc);
diff --git a/src/backend/optimizer/prep/prepsecurity.c b/src/backend/optimizer/prep/prepsecurity.c
index 7daaa33..f5d48dc 100644
--- a/src/backend/optimizer/prep/prepsecurity.c
+++ b/src/backend/optimizer/prep/prepsecurity.c
@@ -230,19 +230,19 @@ expand_security_qual(PlannerInfo *root, List *tlist, int rt_index,
{
case ROW_MARK_EXCLUSIVE:
applyLockingClause(subquery, 1, LCS_FORUPDATE,
- rc->noWait, false);
+ rc->noWait, rc->skipLocked, false);
break;
case ROW_MARK_NOKEYEXCLUSIVE:
applyLockingClause(subquery, 1, LCS_FORNOKEYUPDATE,
- rc->noWait, false);
+ rc->noWait, rc->skipLocked, false);
break;
case ROW_MARK_SHARE:
applyLockingClause(subquery, 1, LCS_FORSHARE,
- rc->noWait, false);
+ rc->noWait, rc->skipLocked, false);
break;
case ROW_MARK_KEYSHARE:
applyLockingClause(subquery, 1, LCS_FORKEYSHARE,
- rc->noWait, false);
+ rc->noWait, rc->skipLocked, false);
break;
case ROW_MARK_REFERENCE:
case ROW_MARK_COPY:
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 7225bb6..da3ff5c 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -2359,6 +2359,7 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
allrels->lockedRels = NIL; /* indicates all rels */
allrels->strength = lc->strength;
allrels->noWait = lc->noWait;
+ allrels->skipLocked = lc->skipLocked;
if (lockedRels == NIL)
{
@@ -2373,12 +2374,12 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
{
case RTE_RELATION:
applyLockingClause(qry, i,
- lc->strength, lc->noWait, pushedDown);
+ lc->strength, lc->noWait, lc->skipLocked, pushedDown);
rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
break;
case RTE_SUBQUERY:
applyLockingClause(qry, i,
- lc->strength, lc->noWait, pushedDown);
+ lc->strength, lc->noWait, lc->skipLocked, pushedDown);
/*
* FOR UPDATE/SHARE of subquery is propagated to all of
@@ -2425,13 +2426,13 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
{
case RTE_RELATION:
applyLockingClause(qry, i,
- lc->strength, lc->noWait,
+ lc->strength, lc->noWait, lc->skipLocked,
pushedDown);
rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
break;
case RTE_SUBQUERY:
applyLockingClause(qry, i,
- lc->strength, lc->noWait,
+ lc->strength, lc->noWait, lc->skipLocked,
pushedDown);
/* see comment above */
transformLockingClause(pstate, rte->subquery,
@@ -2499,7 +2500,7 @@ transformLockingClause(ParseState *pstate, Query *qry, LockingClause *lc,
*/
void
applyLockingClause(Query *qry, Index rtindex,
- LockClauseStrength strength, bool noWait, bool pushedDown)
+ LockClauseStrength strength, bool noWait, bool skipLocked, bool pushedDown)
{
RowMarkClause *rc;
@@ -2524,7 +2525,12 @@ applyLockingClause(Query *qry, Index rtindex,
* And of course pushedDown becomes false if any clause is explicit.
*/
rc->strength = Max(rc->strength, strength);
- rc->noWait |= noWait;
+ if (noWait) { /* TODO combine into one enum! */
+ rc->noWait = true;
+ rc->skipLocked = false;
+ } else if (skipLocked && !rc->skipLocked) {
+ rc->skipLocked = true;
+ }
rc->pushedDown &= pushedDown;
return;
}
@@ -2534,6 +2540,7 @@ applyLockingClause(Query *qry, Index rtindex,
rc->rti = rtindex;
rc->strength = strength;
rc->noWait = noWait;
+ rc->skipLocked = skipLocked;
rc->pushedDown = pushedDown;
qry->rowMarks = lappend(qry->rowMarks, rc);
}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7b9895d..2092140 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -119,6 +119,9 @@ typedef struct PrivTarget
#define CAS_NOT_VALID 0x10
#define CAS_NO_INHERIT 0x20
+#define WAIT_MODE_DEFAULT 0
+#define WAIT_MODE_NOWAIT 1
+#define WAIT_MODE_SKIP 2
#define parser_yyerror(msg) scanner_yyerror(msg, yyscanner)
#define parser_errposition(pos) scanner_errposition(pos, yyscanner)
@@ -273,6 +276,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type opt_force opt_or_replace
opt_grant_grant_option opt_grant_admin_option
opt_nowait opt_if_exists opt_with_data
+%type opt_nowait_or_skip
%type OptRoleList AlterOptRoleList
%type CreateOptRoleElem AlterOptRoleElem
@@ -563,7 +567,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
LABEL LANGUAGE LARGE_P LAST_P LATERAL_P LC_COLLATE_P LC_CTYPE_P
LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
- LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P
+ LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED
MAPPING MATCH MATERIALIZED MAXVALUE MINUTE_P MINVALUE MODE MONTH_P MOVE
@@ -587,7 +591,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
SERIALIZABLE SERVER SESSION SESSION_USER SET SETOF SHARE
- SHOW SIMILAR SIMPLE SMALLINT SNAPSHOT SOME STABLE STANDALONE_P START
+ SHOW SIMILAR SIMPLE SKIP SMALLINT SNAPSHOT SOME STABLE STANDALONE_P START
STATEMENT STATISTICS STDIN STDOUT STORAGE STRICT_P STRIP_P SUBSTRING
SYMMETRIC SYSID SYSTEM_P
@@ -9188,6 +9192,12 @@ opt_nowait: NOWAIT { $$ = TRUE; }
| /*EMPTY*/ { $$ = FALSE; }
;
+opt_nowait_or_skip:
+ NOWAIT { $$ = WAIT_MODE_NOWAIT; }
+ | SKIP LOCKED DATA_P { $$ = WAIT_MODE_SKIP; }
+ | /*EMPTY*/ { $$ = WAIT_MODE_DEFAULT; }
+ ;
+
/*****************************************************************************
*
@@ -9790,12 +9800,13 @@ for_locking_items:
;
for_locking_item:
- for_locking_strength locked_rels_list opt_nowait
+ for_locking_strength locked_rels_list opt_nowait_or_skip
{
LockingClause *n = makeNode(LockingClause);
n->lockedRels = $2;
n->strength = $1;
- n->noWait = $3;
+ n->noWait = ($3 == WAIT_MODE_NOWAIT);
+ n->skipLocked = ($3 == WAIT_MODE_SKIP);
$$ = (Node *) n;
}
;
@@ -12921,6 +12932,7 @@ unreserved_keyword:
| LOCAL
| LOCATION
| LOCK_P
+ | LOCKED
| MAPPING
| MATCH
| MATERIALIZED
@@ -13003,6 +13015,7 @@ unreserved_keyword:
| SHARE
| SHOW
| SIMPLE
+ | SKIP
| SNAPSHOT
| STABLE
| STANDALONE_P
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index caed8ca..717e880 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -62,7 +62,7 @@ static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation,
static void rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
Relation target_relation);
static void markQueryForLocking(Query *qry, Node *jtnode,
- LockClauseStrength strength, bool noWait, bool pushedDown);
+ LockClauseStrength strength, bool noWait, bool skipLocked, bool pushedDown);
static List *matchLocks(CmdType event, RuleLock *rulelocks,
int varno, Query *parsetree);
static Query *fireRIRrules(Query *parsetree, List *activeRIRs,
@@ -1481,7 +1481,7 @@ ApplyRetrieveRule(Query *parsetree,
*/
if (rc != NULL)
markQueryForLocking(rule_action, (Node *) rule_action->jointree,
- rc->strength, rc->noWait, true);
+ rc->strength, rc->noWait, rc->skipLocked, true);
return parsetree;
}
@@ -1499,7 +1499,7 @@ ApplyRetrieveRule(Query *parsetree,
*/
static void
markQueryForLocking(Query *qry, Node *jtnode,
- LockClauseStrength strength, bool noWait, bool pushedDown)
+ LockClauseStrength strength, bool noWait, bool skipLocked, bool pushedDown)
{
if (jtnode == NULL)
return;
@@ -1510,15 +1510,15 @@ markQueryForLocking(Query *qry, Node *jtnode,
if (rte->rtekind == RTE_RELATION)
{
- applyLockingClause(qry, rti, strength, noWait, pushedDown);
+ applyLockingClause(qry, rti, strength, noWait, skipLocked, pushedDown);
rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
}
else if (rte->rtekind == RTE_SUBQUERY)
{
- applyLockingClause(qry, rti, strength, noWait, pushedDown);
+ applyLockingClause(qry, rti, strength, noWait, skipLocked, pushedDown);
/* FOR UPDATE/SHARE of subquery is propagated to subquery's rels */
markQueryForLocking(rte->subquery, (Node *) rte->subquery->jointree,
- strength, noWait, true);
+ strength, noWait, skipLocked, true);
}
/* other RTE types are unaffected by FOR UPDATE */
}
@@ -1528,14 +1528,14 @@ markQueryForLocking(Query *qry, Node *jtnode,
ListCell *l;
foreach(l, f->fromlist)
- markQueryForLocking(qry, lfirst(l), strength, noWait, pushedDown);
+ markQueryForLocking(qry, lfirst(l), strength, noWait, skipLocked, pushedDown);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
- markQueryForLocking(qry, j->larg, strength, noWait, pushedDown);
- markQueryForLocking(qry, j->rarg, strength, noWait, pushedDown);
+ markQueryForLocking(qry, j->larg, strength, noWait, skipLocked, pushedDown);
+ markQueryForLocking(qry, j->rarg, strength, noWait, skipLocked, pushedDown);
}
else
elog(ERROR, "unrecognized node type: %d",
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 0f80257..bf1d1f5 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -22,6 +22,12 @@
#include "utils/relcache.h"
#include "utils/snapshot.h"
+typedef enum
+{
+ LockWaitBlock,
+ LockWaitError,
+ LockWaitSkip
+} LockWaitPolicy;
/* "options" flag bits for heap_insert */
#define HEAP_INSERT_SKIP_WAL 0x0001
@@ -144,7 +150,7 @@ extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
CommandId cid, Snapshot crosscheck, bool wait,
HeapUpdateFailureData *hufd, LockTupleMode *lockmode);
extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
- CommandId cid, LockTupleMode mode, bool nowait,
+ CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
bool follow_update,
Buffer *buffer, HeapUpdateFailureData *hufd);
extern void heap_inplace_update(Relation relation, HeapTuple tuple);
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 6c94e8a..179d48b 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -430,6 +430,7 @@ typedef struct ExecRowMark
Index rowmarkId; /* unique identifier for resjunk columns */
RowMarkType markType; /* see enum in nodes/plannodes.h */
bool noWait; /* NOWAIT option */
+ bool skipLocked; /* SKIP LOCKED DATA option */
ItemPointerData curCtid; /* ctid of currently locked tuple, if any */
} ExecRowMark;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 18d4991..2a77a33 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -617,6 +617,7 @@ typedef struct LockingClause
List *lockedRels; /* FOR [KEY] UPDATE/SHARE relations */
LockClauseStrength strength;
bool noWait; /* NOWAIT option */
+ bool skipLocked; /* SKIP LOCKED DATA option */
} LockingClause;
/*
@@ -962,6 +963,7 @@ typedef struct RowMarkClause
Index rti; /* range table index of target relation */
LockClauseStrength strength;
bool noWait; /* NOWAIT option */
+ bool skipLocked; /* SKIP LOCKED DATA option */
bool pushedDown; /* pushed down from higher query level? */
} RowMarkClause;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 38c039c..b90537d 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -832,6 +832,7 @@ typedef struct PlanRowMark
Index rowmarkId; /* unique identifier for resjunk columns */
RowMarkType markType; /* see enum above */
bool noWait; /* NOWAIT option */
+ bool skipLocked; /* SKIP LOCKED DATA option */
bool isParent; /* true if this is a "dummy" parent entry */
} PlanRowMark;
diff --git a/src/include/parser/analyze.h b/src/include/parser/analyze.h
index 370a445..16bc59c 100644
--- a/src/include/parser/analyze.h
+++ b/src/include/parser/analyze.h
@@ -39,6 +39,6 @@ extern bool analyze_requires_snapshot(Node *parseTree);
extern char *LCS_asString(LockClauseStrength strength);
extern void CheckSelectLocking(Query *qry, LockClauseStrength strength);
extern void applyLockingClause(Query *qry, Index rtindex,
- LockClauseStrength strength, bool noWait, bool pushedDown);
+ LockClauseStrength strength, bool noWait, bool skipLocked, bool pushedDown);
#endif /* ANALYZE_H */
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 61fae22..969c27c 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -231,6 +231,7 @@ PG_KEYWORD("localtime", LOCALTIME, RESERVED_KEYWORD)
PG_KEYWORD("localtimestamp", LOCALTIMESTAMP, RESERVED_KEYWORD)
PG_KEYWORD("location", LOCATION, UNRESERVED_KEYWORD)
PG_KEYWORD("lock", LOCK_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("locked", LOCKED, UNRESERVED_KEYWORD)
PG_KEYWORD("mapping", MAPPING, UNRESERVED_KEYWORD)
PG_KEYWORD("match", MATCH, UNRESERVED_KEYWORD)
PG_KEYWORD("materialized", MATERIALIZED, UNRESERVED_KEYWORD)
@@ -344,6 +345,7 @@ PG_KEYWORD("share", SHARE, UNRESERVED_KEYWORD)
PG_KEYWORD("show", SHOW, UNRESERVED_KEYWORD)
PG_KEYWORD("similar", SIMILAR, TYPE_FUNC_NAME_KEYWORD)
PG_KEYWORD("simple", SIMPLE, UNRESERVED_KEYWORD)
+PG_KEYWORD("skip", SKIP, UNRESERVED_KEYWORD)
PG_KEYWORD("smallint", SMALLINT, COL_NAME_KEYWORD)
PG_KEYWORD("snapshot", SNAPSHOT, UNRESERVED_KEYWORD)
PG_KEYWORD("some", SOME, RESERVED_KEYWORD)
diff --git a/src/include/utils/snapshot.h b/src/include/utils/snapshot.h
index 8ee9285..f931404 100644
--- a/src/include/utils/snapshot.h
+++ b/src/include/utils/snapshot.h
@@ -102,7 +102,8 @@ typedef enum
HeapTupleInvisible,
HeapTupleSelfUpdated,
HeapTupleUpdated,
- HeapTupleBeingUpdated
+ HeapTupleBeingUpdated,
+ HeapTupleWouldBlock /* can be returned by heap_tuple_lock */
} HTSU_Result;
#endif /* SNAPSHOT_H */
diff --git a/src/test/isolation/expected/skip-locked-data.out b/src/test/isolation/expected/skip-locked-data.out
new file mode 100644
index 0000000..dd34500
--- /dev/null
+++ b/src/test/isolation/expected/skip-locked-data.out
@@ -0,0 +1,401 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1a s1b s1c s2a s2b s2c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+
+starting permutation: s1a s1b s2a s1c s2b s2c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1c: COMMIT;
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+
+starting permutation: s1a s1b s2a s2b s1c s2c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1c: COMMIT;
+step s2c: COMMIT;
+
+starting permutation: s1a s1b s2a s2b s2c s1c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2c: COMMIT;
+step s1c: COMMIT;
+
+starting permutation: s1a s2a s1b s1c s2b s2c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+
+starting permutation: s1a s2a s1b s2b s1c s2c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1c: COMMIT;
+step s2c: COMMIT;
+
+starting permutation: s1a s2a s1b s2b s2c s1c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2c: COMMIT;
+step s1c: COMMIT;
+
+starting permutation: s1a s2a s2b s1b s1c s2c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+step s2c: COMMIT;
+
+starting permutation: s1a s2a s2b s1b s2c s1c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+step s1c: COMMIT;
+
+starting permutation: s1a s2a s2b s2c s1b s1c
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2c: COMMIT;
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+
+starting permutation: s2a s1a s1b s1c s2b s2c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1c: COMMIT;
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+
+starting permutation: s2a s1a s1b s2b s1c s2c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+step s2c: COMMIT;
+
+starting permutation: s2a s1a s1b s2b s2c s1c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+step s1c: COMMIT;
+
+starting permutation: s2a s1a s2b s1b s1c s2c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1c: COMMIT;
+step s2c: COMMIT;
+
+starting permutation: s2a s1a s2b s1b s2c s1c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2c: COMMIT;
+step s1c: COMMIT;
+
+starting permutation: s2a s1a s2b s2c s1b s1c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+
+starting permutation: s2a s2b s1a s1b s1c s2c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1c: COMMIT;
+step s2c: COMMIT;
+
+starting permutation: s2a s2b s1a s1b s2c s1c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2c: COMMIT;
+step s1c: COMMIT;
+
+starting permutation: s2a s2b s1a s2c s1b s1c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+2 bar NEW
+step s2c: COMMIT;
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
+
+starting permutation: s2a s2b s2c s1a s1b s1c
+step s2a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s2c: COMMIT;
+step s1a: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1b: SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1;
+id data status
+
+1 foo NEW
+step s1c: COMMIT;
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index 36acec1..fc868cf 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -25,3 +25,4 @@ test: propagate-lock-delete
test: drop-index-concurrently-1
test: alter-table-1
test: timeouts
+test: skip-locked-data
diff --git a/src/test/isolation/specs/skip-locked-data.spec b/src/test/isolation/specs/skip-locked-data.spec
new file mode 100644
index 0000000..8116cb4
--- /dev/null
+++ b/src/test/isolation/specs/skip-locked-data.spec
@@ -0,0 +1,26 @@
+setup
+{
+ CREATE TABLE queue (
+ id int PRIMARY KEY,
+ data text NOT NULL,
+ status text NOT NULL
+ );
+ INSERT INTO queue VALUES (1, 'foo', 'NEW'), (2, 'bar', 'NEW');
+}
+
+teardown
+{
+ DROP TABLE queue;
+}
+
+session "s1"
+setup { BEGIN; }
+step "s1a" { SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1; }
+step "s1b" { SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1; }
+step "s1c" { COMMIT; }
+
+session "s2"
+setup { BEGIN; }
+step "s2a" { SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1; }
+step "s2b" { SELECT * FROM queue ORDER BY id FOR UPDATE SKIP LOCKED DATA LIMIT 1; }
+step "s2c" { COMMIT; }