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HOT updates. When we update a tuple without changing any of its indexed

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columns, and the new version can be stored on the same heap page, we no longer
generate extra index entries for the new version.  Instead, index searches
follow the HOT-chain links to ensure they find the correct tuple version.

In addition, this patch introduces the ability to "prune" dead tuples on a
per-page basis, without having to do a complete VACUUM pass to recover space.
VACUUM is still needed to clean up dead index entries, however.

Pavan Deolasee, with help from a bunch of other people.
This commit is contained in:
Tom Lane
2007-09-20 17:56:33 +00:00
parent bbf4fdc253
commit 282d2a03dd
65 changed files with 3517 additions and 514 deletions
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42
src/backend/utils/cache/plancache.c vendored
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@ -33,13 +33,14 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.10 2007/06/05 20:00:41 wieck Exp $
* $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.11 2007/09/20 17:56:31 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "utils/plancache.h"
#include "access/transam.h"
#include "catalog/namespace.h"
#include "executor/executor.h"
#include "optimizer/clauses.h"
@ -79,6 +80,7 @@ static void ScanQueryForRelids(Query *parsetree,
void *arg);
static bool ScanQueryWalker(Node *node, ScanQueryWalkerContext *context);
static bool rowmark_member(List *rowMarks, int rt_index);
static bool plan_list_is_transient(List *stmt_list);
static void PlanCacheCallback(Datum arg, Oid relid);
static void InvalRelid(Oid relid, LOCKMODE lockmode,
InvalRelidContext *context);
@ -322,6 +324,13 @@ StoreCachedPlan(CachedPlanSource *plansource,
plan->stmt_list = stmt_list;
plan->fully_planned = plansource->fully_planned;
plan->dead = false;
if (plansource->fully_planned && plan_list_is_transient(stmt_list))
{
Assert(TransactionIdIsNormal(TransactionXmin));
plan->saved_xmin = TransactionXmin;
}
else
plan->saved_xmin = InvalidTransactionId;
plan->refcount = 1; /* for the parent's link */
plan->generation = ++(plansource->generation);
plan->context = plan_context;
@ -411,6 +420,15 @@ RevalidateCachedPlan(CachedPlanSource *plansource, bool useResOwner)
else
AcquirePlannerLocks(plan->stmt_list, true);
/*
* If plan was transient, check to see if TransactionXmin has
* advanced, and if so invalidate it.
*/
if (!plan->dead &&
TransactionIdIsValid(plan->saved_xmin) &&
!TransactionIdEquals(plan->saved_xmin, TransactionXmin))
plan->dead = true;
/*
* By now, if any invalidation has happened, PlanCacheCallback
* will have marked the plan dead.
@ -789,6 +807,28 @@ rowmark_member(List *rowMarks, int rt_index)
return false;
}
/*
* plan_list_is_transient: check if any of the plans in the list are transient.
*/
static bool
plan_list_is_transient(List *stmt_list)
{
ListCell *lc;
foreach(lc, stmt_list)
{
PlannedStmt *plannedstmt = (PlannedStmt *) lfirst(lc);
if (!IsA(plannedstmt, PlannedStmt))
continue; /* Ignore utility statements */
if (plannedstmt->transientPlan)
return true;
}
return false;
}
/*
* PlanCacheComputeResultDesc: given a list of either fully-planned statements
* or Queries, determine the result tupledesc it will produce. Returns NULL