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Implement sharable row-level locks, and use them for foreign key references

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to eliminate unnecessary deadlocks.  This commit adds SELECT ... FOR SHARE
paralleling SELECT ... FOR UPDATE.  The implementation uses a new SLRU
data structure (managed much like pg_subtrans) to represent multiple-
transaction-ID sets.  When more than one transaction is holding a shared
lock on a particular row, we create a MultiXactId representing that set
of transactions and store its ID in the row's XMAX.  This scheme allows
an effectively unlimited number of row locks, just as we did before,
while not costing any extra overhead except when a shared lock actually
has to be shared.   Still TODO: use the regular lock manager to control
the grant order when multiple backends are waiting for a row lock.

Alvaro Herrera and Tom Lane.
This commit is contained in:
Tom Lane
2005-04-28 21:47:18 +00:00
parent d902e7d63b
commit bedb78d386
55 changed files with 2802 additions and 439 deletions
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104
src/backend/parser/analyze.c
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@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/backend/parser/analyze.c,v 1.320 2005/04/14 20:03:24 tgl Exp $
* $PostgreSQL: pgsql/src/backend/parser/analyze.c,v 1.321 2005/04/28 21:47:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -134,7 +134,7 @@ static void transformFKConstraints(ParseState *pstate,
bool isAddConstraint);
static void applyColumnNames(List *dst, List *src);
static List *getSetColTypes(ParseState *pstate, Node *node);
static void transformForUpdate(Query *qry, List *forUpdate);
static void transformLocking(Query *qry, List *lockedRels, bool forUpdate);
static void transformConstraintAttrs(List *constraintList);
static void transformColumnType(ParseState *pstate, ColumnDef *column);
static void release_pstate_resources(ParseState *pstate);
@ -1810,8 +1810,8 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
qry->commandType = CMD_SELECT;
/* make FOR UPDATE clause available to addRangeTableEntry */
pstate->p_forUpdate = stmt->forUpdate;
/* make FOR UPDATE/FOR SHARE list available to addRangeTableEntry */
pstate->p_lockedRels = stmt->lockedRels;
/* process the FROM clause */
transformFromClause(pstate, stmt->fromClause);
@ -1870,8 +1870,8 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
if (pstate->p_hasAggs || qry->groupClause || qry->havingQual)
parseCheckAggregates(pstate, qry);
if (stmt->forUpdate != NIL)
transformForUpdate(qry, stmt->forUpdate);
if (stmt->lockedRels != NIL)
transformLocking(qry, stmt->lockedRels, stmt->forUpdate);
return qry;
}
@ -1899,7 +1899,8 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
List *sortClause;
Node *limitOffset;
Node *limitCount;
List *forUpdate;
List *lockedRels;
bool forUpdate;
Node *node;
ListCell *left_tlist,
*dtlist;
@ -1937,18 +1938,19 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
sortClause = stmt->sortClause;
limitOffset = stmt->limitOffset;
limitCount = stmt->limitCount;
lockedRels = stmt->lockedRels;
forUpdate = stmt->forUpdate;
stmt->sortClause = NIL;
stmt->limitOffset = NULL;
stmt->limitCount = NULL;
stmt->forUpdate = NIL;
stmt->lockedRels = NIL;
/* We don't support forUpdate with set ops at the moment. */
if (forUpdate)
/* We don't support FOR UPDATE/SHARE with set ops at the moment. */
if (lockedRels)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT")));
errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
/*
* Recursively transform the components of the tree.
@ -2083,8 +2085,8 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
if (pstate->p_hasAggs || qry->groupClause || qry->havingQual)
parseCheckAggregates(pstate, qry);
if (forUpdate != NIL)
transformForUpdate(qry, forUpdate);
if (lockedRels != NIL)
transformLocking(qry, lockedRels, forUpdate);
return qry;
}
@ -2107,11 +2109,11 @@ transformSetOperationTree(ParseState *pstate, SelectStmt *stmt)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("INTO is only allowed on first SELECT of UNION/INTERSECT/EXCEPT")));
/* We don't support forUpdate with set ops at the moment. */
if (stmt->forUpdate)
/* We don't support FOR UPDATE/SHARE with set ops at the moment. */
if (stmt->lockedRels)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT")));
errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
/*
* If an internal node of a set-op tree has ORDER BY, UPDATE, or LIMIT
@ -2128,7 +2130,7 @@ transformSetOperationTree(ParseState *pstate, SelectStmt *stmt)
{
Assert(stmt->larg != NULL && stmt->rarg != NULL);
if (stmt->sortClause || stmt->limitOffset || stmt->limitCount ||
stmt->forUpdate)
stmt->lockedRels)
isLeaf = true;
else
isLeaf = false;
@ -2711,47 +2713,67 @@ transformExecuteStmt(ParseState *pstate, ExecuteStmt *stmt)
/* exported so planner can check again after rewriting, query pullup, etc */
void
CheckSelectForUpdate(Query *qry)
CheckSelectLocking(Query *qry, bool forUpdate)
{
const char *operation;
if (forUpdate)
operation = "SELECT FOR UPDATE";
else
operation = "SELECT FOR SHARE";
if (qry->setOperations)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT")));
/* translator: %s is a SQL command, like SELECT FOR UPDATE */
errmsg("%s is not allowed with UNION/INTERSECT/EXCEPT", operation)));
if (qry->distinctClause != NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with DISTINCT clause")));
/* translator: %s is a SQL command, like SELECT FOR UPDATE */
errmsg("%s is not allowed with DISTINCT clause", operation)));
if (qry->groupClause != NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with GROUP BY clause")));
/* translator: %s is a SQL command, like SELECT FOR UPDATE */
errmsg("%s is not allowed with GROUP BY clause", operation)));
if (qry->havingQual != NULL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with HAVING clause")));
/* translator: %s is a SQL command, like SELECT FOR UPDATE */
errmsg("%s is not allowed with HAVING clause", operation)));
if (qry->hasAggs)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE is not allowed with aggregate functions")));
/* translator: %s is a SQL command, like SELECT FOR UPDATE */
errmsg("%s is not allowed with aggregate functions", operation)));
}
/*
* Convert FOR UPDATE name list into rowMarks list of integer relids
* Convert FOR UPDATE/SHARE name list into rowMarks list of integer relids
*
* NB: if you need to change this, see also markQueryForUpdate()
* NB: if you need to change this, see also markQueryForLocking()
* in rewriteHandler.c.
*/
static void
transformForUpdate(Query *qry, List *forUpdate)
transformLocking(Query *qry, List *lockedRels, bool forUpdate)
{
List *rowMarks = qry->rowMarks;
List *rowMarks;
ListCell *l;
ListCell *rt;
Index i;
CheckSelectForUpdate(qry);
if (qry->rowMarks && forUpdate != qry->forUpdate)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot use both FOR UPDATE and FOR SHARE in one query")));
qry->forUpdate = forUpdate;
if (linitial(forUpdate) == NULL)
CheckSelectLocking(qry, forUpdate);
rowMarks = qry->rowMarks;
if (linitial(lockedRels) == NULL)
{
/* all regular tables used in query */
i = 0;
@ -2770,10 +2792,11 @@ transformForUpdate(Query *qry, List *forUpdate)
case RTE_SUBQUERY:
/*
* FOR UPDATE of subquery is propagated to subquery's
* rels
* FOR UPDATE/SHARE of subquery is propagated to all
* of subquery's rels
*/
transformForUpdate(rte->subquery, list_make1(NULL));
transformLocking(rte->subquery, list_make1(NULL),
forUpdate);
break;
default:
/* ignore JOIN, SPECIAL, FUNCTION RTEs */
@ -2784,7 +2807,7 @@ transformForUpdate(Query *qry, List *forUpdate)
else
{
/* just the named tables */
foreach(l, forUpdate)
foreach(l, lockedRels)
{
char *relname = strVal(lfirst(l));
@ -2806,25 +2829,26 @@ transformForUpdate(Query *qry, List *forUpdate)
case RTE_SUBQUERY:
/*
* FOR UPDATE of subquery is propagated to
* subquery's rels
* FOR UPDATE/SHARE of subquery is propagated to
* all of subquery's rels
*/
transformForUpdate(rte->subquery, list_make1(NULL));
transformLocking(rte->subquery, list_make1(NULL),
forUpdate);
break;
case RTE_JOIN:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE cannot be applied to a join")));
errmsg("SELECT FOR UPDATE/SHARE cannot be applied to a join")));
break;
case RTE_SPECIAL:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE cannot be applied to NEW or OLD")));
errmsg("SELECT FOR UPDATE/SHARE cannot be applied to NEW or OLD")));
break;
case RTE_FUNCTION:
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("SELECT FOR UPDATE cannot be applied to a function")));
errmsg("SELECT FOR UPDATE/SHARE cannot be applied to a function")));
break;
default:
elog(ERROR, "unrecognized RTE type: %d",
@ -2837,7 +2861,7 @@ transformForUpdate(Query *qry, List *forUpdate)
if (rt == NULL)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_TABLE),
errmsg("relation \"%s\" in FOR UPDATE clause not found in FROM clause",
errmsg("relation \"%s\" in FOR UPDATE/SHARE clause not found in FROM clause",
relname)));
}
}