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Code review for FETCH/MOVE 0 changes. Improve documentation, do the

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right thing with the destination when FETCH 0 can't return a row,
don't try to stuff LONG_MAX into an int value.
This commit is contained in:
Tom Lane
2003-01-08 00:22:27 +00:00
parent 1bc9e98549
commit 061168d38f
5 changed files with 113 additions and 74 deletions
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88
src/backend/commands/portalcmds.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/portalcmds.c,v 1.7 2002/12/30 15:31:47 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/commands/portalcmds.c,v 1.8 2003/01/08 00:22:27 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -55,7 +55,7 @@ PortalCleanup(Portal portal)
*
* name: name of portal
* forward: forward or backward fetch?
* count: # of tuples to fetch
* count: # of tuples to fetch (INT_MAX means "all"; 0 means "refetch")
* dest: where to send results
* completionTag: points to a buffer of size COMPLETION_TAG_BUFSIZE
* in which to store a command completion status string.
@ -100,18 +100,15 @@ PerformPortalFetch(char *name,
return;
}
/* If zero count, handle specially */
/*
* Zero count means to re-fetch the current row, if any (per SQL92)
*/
if (count == 0)
{
bool on_row = false;
bool on_row;
/* Are we sitting on a row? */
oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
queryDesc = PortalGetQueryDesc(portal);
estate = queryDesc->estate;
if (portal->atStart == false && portal->atEnd == false)
on_row = true;
MemoryContextSwitchTo(oldcontext);
on_row = (portal->atStart == false && portal->atEnd == false);
if (dest == None)
{
@ -122,26 +119,25 @@ PerformPortalFetch(char *name,
}
else
{
/* If we are not on a row, FETCH 0 returns nothing */
if (!on_row)
return;
/* Since we are sitting on a row, return the row */
/* Back up so we can reread the row */
PerformPortalFetch(name, false /* backward */, 1,
None, /* throw away output */
NULL /* do not modify the command tag */);
/* Set up to fetch one row */
count = 1;
forward = true;
/*
* If we are sitting on a row, back up one so we can re-fetch it.
* If we are not sitting on a row, we still have to start up and
* shut down the executor so that the destination is initialized
* and shut down correctly; so keep going. Further down in the
* routine, count == 0 means we will retrieve no row.
*/
if (on_row)
{
PerformPortalFetch(name, false /* backward */, 1L,
None, /* throw away output */
NULL /* do not modify the command tag */);
/* Set up to fetch one row forward */
count = 1;
forward = true;
}
}
}
/* Internally, zero count processes all portal rows */
if (count == LONG_MAX)
count = 0;
/*
* switch into the portal context
*/
@ -185,31 +181,45 @@ PerformPortalFetch(char *name,
*/
if (forward)
{
if (portal->atEnd)
if (portal->atEnd || count == 0)
direction = NoMovementScanDirection;
else
direction = ForwardScanDirection;
ExecutorRun(queryDesc, direction, (long) count);
/* In the executor, zero count processes all portal rows */
if (count == INT_MAX)
count = 0;
if (estate->es_processed > 0)
portal->atStart = false; /* OK to back up now */
if (count <= 0 || (int) estate->es_processed < count)
portal->atEnd = true; /* we retrieved 'em all */
ExecutorRun(queryDesc, direction, count);
if (direction != NoMovementScanDirection)
{
if (estate->es_processed > 0)
portal->atStart = false; /* OK to back up now */
if (count <= 0 || (long) estate->es_processed < count)
portal->atEnd = true; /* we retrieved 'em all */
}
}
else
{
if (portal->atStart)
if (portal->atStart || count == 0)
direction = NoMovementScanDirection;
else
direction = BackwardScanDirection;
ExecutorRun(queryDesc, direction, (long) count);
/* In the executor, zero count processes all portal rows */
if (count == INT_MAX)
count = 0;
if (estate->es_processed > 0)
portal->atEnd = false; /* OK to go forward now */
if (count <= 0 || (int) estate->es_processed < count)
portal->atStart = true; /* we retrieved 'em all */
ExecutorRun(queryDesc, direction, count);
if (direction != NoMovementScanDirection)
{
if (estate->es_processed > 0)
portal->atEnd = false; /* OK to go forward now */
if (count <= 0 || (long) estate->es_processed < count)
portal->atStart = true; /* we retrieved 'em all */
}
}
/* Return command status if wanted */