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Fix problems with cached tuple descriptors disappearing while still in use

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by creating a reference-count mechanism, similar to what we did a long time
ago for catcache entries.  The back branches have an ugly solution involving
lots of extra copies, but this way is more efficient.  Reference counting is
only applied to tupdescs that are actually in caches --- there seems no need
to use it for tupdescs that are generated in the executor, since they'll go
away during plan shutdown by virtue of being in the per-query memory context.
Neil Conway and Tom Lane
This commit is contained in:
Tom Lane
2006-06-16 18:42:24 +00:00
parent b49ce32da1
commit 06e10abc0b
36 changed files with 581 additions and 246 deletions
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34
src/backend/executor/execTuples.c
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@ -15,7 +15,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/execTuples.c,v 1.93 2006/04/04 19:35:34 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/execTuples.c,v 1.94 2006/06/16 18:42:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -143,7 +143,6 @@ ExecCreateTupleTable(int tableSize)
slot->type = T_TupleTableSlot;
slot->tts_isempty = true;
slot->tts_shouldFree = false;
slot->tts_shouldFreeDesc = false;
slot->tts_tuple = NULL;
slot->tts_tupleDescriptor = NULL;
slot->tts_mcxt = CurrentMemoryContext;
@ -189,8 +188,8 @@ ExecDropTupleTable(TupleTable table, /* tuple table */
TupleTableSlot *slot = &(table->array[i]);
ExecClearTuple(slot);
if (slot->tts_shouldFreeDesc)
FreeTupleDesc(slot->tts_tupleDescriptor);
if (slot->tts_tupleDescriptor)
ReleaseTupleDesc(slot->tts_tupleDescriptor);
if (slot->tts_values)
pfree(slot->tts_values);
if (slot->tts_isnull)
@ -210,7 +209,7 @@ ExecDropTupleTable(TupleTable table, /* tuple table */
* This is a convenience routine for operations that need a
* standalone TupleTableSlot not gotten from the main executor
* tuple table. It makes a single slot and initializes it as
* though by ExecSetSlotDescriptor(slot, tupdesc, false).
* though by ExecSetSlotDescriptor(slot, tupdesc).
* --------------------------------
*/
TupleTableSlot *
@ -221,7 +220,6 @@ MakeSingleTupleTableSlot(TupleDesc tupdesc)
/* This should match ExecCreateTupleTable() */
slot->tts_isempty = true;
slot->tts_shouldFree = false;
slot->tts_shouldFreeDesc = false;
slot->tts_tuple = NULL;
slot->tts_tupleDescriptor = NULL;
slot->tts_mcxt = CurrentMemoryContext;
@ -230,7 +228,7 @@ MakeSingleTupleTableSlot(TupleDesc tupdesc)
slot->tts_values = NULL;
slot->tts_isnull = NULL;
ExecSetSlotDescriptor(slot, tupdesc, false);
ExecSetSlotDescriptor(slot, tupdesc);
return slot;
}
@ -250,8 +248,8 @@ ExecDropSingleTupleTableSlot(TupleTableSlot *slot)
Assert(slot != NULL);
ExecClearTuple(slot);
if (slot->tts_shouldFreeDesc)
FreeTupleDesc(slot->tts_tupleDescriptor);
if (slot->tts_tupleDescriptor)
ReleaseTupleDesc(slot->tts_tupleDescriptor);
if (slot->tts_values)
pfree(slot->tts_values);
if (slot->tts_isnull)
@ -309,13 +307,15 @@ ExecAllocTableSlot(TupleTable table)
* ExecSetSlotDescriptor
*
* This function is used to set the tuple descriptor associated
* with the slot's tuple.
* with the slot's tuple. The passed descriptor must have lifespan
* at least equal to the slot's. If it is a reference-counted descriptor
* then the reference count is incremented for as long as the slot holds
* a reference.
* --------------------------------
*/
void
ExecSetSlotDescriptor(TupleTableSlot *slot, /* slot to change */
TupleDesc tupdesc, /* new tuple descriptor */
bool shouldFree) /* is desc owned by slot? */
TupleDesc tupdesc) /* new tuple descriptor */
{
/* For safety, make sure slot is empty before changing it */
ExecClearTuple(slot);
@ -324,8 +324,8 @@ ExecSetSlotDescriptor(TupleTableSlot *slot, /* slot to change */
* Release any old descriptor. Also release old Datum/isnull arrays if
* present (we don't bother to check if they could be re-used).
*/
if (slot->tts_shouldFreeDesc)
FreeTupleDesc(slot->tts_tupleDescriptor);
if (slot->tts_tupleDescriptor)
ReleaseTupleDesc(slot->tts_tupleDescriptor);
if (slot->tts_values)
pfree(slot->tts_values);
@ -333,10 +333,10 @@ ExecSetSlotDescriptor(TupleTableSlot *slot, /* slot to change */
pfree(slot->tts_isnull);
/*
* Set up the new descriptor
* Install the new descriptor; if it's refcounted, bump its refcount.
*/
slot->tts_tupleDescriptor = tupdesc;
slot->tts_shouldFreeDesc = shouldFree;
PinTupleDesc(tupdesc);
/*
* Allocate Datum/isnull arrays of the appropriate size. These must have
@ -740,7 +740,7 @@ ExecInitNullTupleSlot(EState *estate, TupleDesc tupType)
{
TupleTableSlot *slot = ExecInitExtraTupleSlot(estate);
ExecSetSlotDescriptor(slot, tupType, false);
ExecSetSlotDescriptor(slot, tupType);
return ExecStoreAllNullTuple(slot);
}