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Keep track of the last active slot in the shared ProcState array, so

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that search loops only have to scan that far and not through all maxBackends
entries.  This eliminates a performance penalty for setting maxBackends
much higher than the average number of active backends.  Also, eliminate
no-longer-used 'backend tag' concept.  Remove setting of environment
variables at backend start (except for CYR_RECODE), since none of them
are being examined by the backend any longer.
This commit is contained in:
Tom Lane
2000-11-12 20:51:52 +00:00
parent c48025e799
commit ebb0a20149
10 changed files with 153 additions and 235 deletions
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24
src/backend/storage/ipc/sinval.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.22 2000/11/05 22:50:20 vadim Exp $
* $Header: /cvsroot/pgsql/src/backend/storage/ipc/sinval.c,v 1.23 2000/11/12 20:51:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -185,6 +185,9 @@ void
/*
* DatabaseHasActiveBackends -- are there any backends running in the given DB
*
* If 'ignoreMyself' is TRUE, ignore this particular backend while checking
* for backends in the target database.
*
* This function is used to interlock DROP DATABASE against there being
* any active backends in the target DB --- dropping the DB while active
* backends remain would be a Bad Thing. Note that we cannot detect here
@@ -194,7 +197,7 @@ void
*/
bool
DatabaseHasActiveBackends(Oid databaseId)
DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself)
{
bool result = false;
SISeg *segP = shmInvalBuffer;
@@ -203,7 +206,7 @@ DatabaseHasActiveBackends(Oid databaseId)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -213,6 +216,9 @@ DatabaseHasActiveBackends(Oid databaseId)
if (proc->databaseId == databaseId)
{
if (ignoreMyself && proc == MyProc)
continue;
result = true;
break;
}
@@ -237,7 +243,7 @@ TransactionIdIsInProgress(TransactionId xid)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -275,7 +281,7 @@ GetXmaxRecent(TransactionId *XmaxRecent)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -309,11 +315,11 @@ GetSnapshotData(bool serializable)
int count = 0;
/*
* There can be no more than maxBackends active transactions, so this
* There can be no more than lastBackend active transactions, so this
* is enough space:
*/
snapshot->xip = (TransactionId *)
malloc(segP->maxBackends * sizeof(TransactionId));
malloc(segP->lastBackend * sizeof(TransactionId));
snapshot->xmin = GetCurrentTransactionId();
SpinAcquire(SInvalLock);
@@ -326,7 +332,7 @@ GetSnapshotData(bool serializable)
*/
ReadNewTransactionId(&(snapshot->xmax));
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
@@ -386,7 +392,7 @@ GetUndoRecPtr(void)
SpinAcquire(SInvalLock);
for (index = 0; index < segP->maxBackends; index++)
for (index = 0; index < segP->lastBackend; index++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;