database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-17 17:02:08 +03:00
Code Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

18
src/backend/parser/parse_relation.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.106 2005/04/13 16:50:55 tgl Exp $
* $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.107 2005/04/28 21:47:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -40,7 +40,7 @@ static Node *scanNameSpaceForRelid(ParseState *pstate, Node *nsnode,
Oid relid);
static void scanNameSpaceForConflict(ParseState *pstate, Node *nsnode,
RangeTblEntry *rte1, const char *aliasname1);
static bool isForUpdate(ParseState *pstate, char *refname);
static bool isLockedRel(ParseState *pstate, char *refname);
static void expandRelation(Oid relid, Alias *eref,
int rtindex, int sublevels_up,
bool include_dropped,
@ -759,9 +759,9 @@ addRangeTableEntry(ParseState *pstate,
* Get the rel's OID. This access also ensures that we have an
* up-to-date relcache entry for the rel. Since this is typically the
* first access to a rel in a statement, be careful to get the right
* access level depending on whether we're doing SELECT FOR UPDATE.
* access level depending on whether we're doing SELECT FOR UPDATE/SHARE.
*/
lockmode = isForUpdate(pstate, refname) ? RowShareLock : AccessShareLock;
lockmode = isLockedRel(pstate, refname) ? RowShareLock : AccessShareLock;
rel = heap_openrv(relation, lockmode);
rte->relid = RelationGetRelid(rel);
@ -1121,17 +1121,17 @@ addRangeTableEntryForJoin(ParseState *pstate,
}
/*
* Has the specified refname been selected FOR UPDATE?
* Has the specified refname been selected FOR UPDATE/FOR SHARE?
*/
static bool
isForUpdate(ParseState *pstate, char *refname)
isLockedRel(ParseState *pstate, char *refname)
{
/* Outer loop to check parent query levels as well as this one */
while (pstate != NULL)
{
if (pstate->p_forUpdate != NIL)
if (pstate->p_lockedRels != NIL)
{
if (linitial(pstate->p_forUpdate) == NULL)
if (linitial(pstate->p_lockedRels) == NULL)
{
/* all tables used in query */
return true;
@ -1141,7 +1141,7 @@ isForUpdate(ParseState *pstate, char *refname)
/* just the named tables */
ListCell *l;
foreach(l, pstate->p_forUpdate)
foreach(l, pstate->p_lockedRels)
{
char *rname = strVal(lfirst(l));