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/*-------------------------------------------------------------------------
*
* tuptable.h
* tuple table support stuff
*
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/executor/tuptable.h,v 1.27 2005/03/14 04:41:13 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef TUPTABLE_H
#define TUPTABLE_H
#include "access/htup.h"
/*
* The executor stores pointers to tuples in a "tuple table"
* which is composed of TupleTableSlots. Sometimes the tuples
* are pointers to buffer pages, while others are pointers to
* palloc'ed memory; the shouldFree variable tells us whether
* we may call pfree() on a tuple. When shouldFree is true,
* the tuple is "owned" by the TupleTableSlot and should be
* freed when the slot's reference to the tuple is dropped.
*
* shouldFreeDesc is similar to shouldFree: if it's true, then the
* tupleDescriptor is "owned" by the TupleTableSlot and should be
* freed when the slot's reference to the descriptor is dropped.
*
* If buffer is not InvalidBuffer, then the slot is holding a pin
* on the indicated buffer page; drop the pin when we release the
* slot's reference to that buffer. (shouldFree should always be
* false in such a case, since presumably val is pointing at the
* buffer page.)
*
* The slot_getattr() routine allows extraction of attribute values from
* a TupleTableSlot's current tuple. It is equivalent to heap_getattr()
* except that it can optimize fetching of multiple values more efficiently.
* The cache_xxx fields of TupleTableSlot are support for slot_getattr().
*/
typedef struct TupleTableSlot
{
NodeTag type; /* vestigial ... allows IsA tests */
HeapTuple val; /* current tuple, or NULL if none */
TupleDesc ttc_tupleDescriptor; /* tuple's descriptor */
bool ttc_shouldFree; /* should pfree tuple? */
bool ttc_shouldFreeDesc; /* should pfree descriptor? */
Buffer ttc_buffer; /* tuple's buffer, or InvalidBuffer */
MemoryContext ttc_mcxt; /* slot itself is in this context */
Datum *cache_values; /* currently extracted values */
int cache_natts; /* # of valid values in cache_values */
bool cache_slow; /* saved state for slot_getattr */
long cache_off; /* saved state for slot_getattr */
} TupleTableSlot;
/*
* Tuple table data structure: an array of TupleTableSlots.
*/
typedef struct TupleTableData
{
int size; /* size of the table (number of slots) */
int next; /* next available slot number */
TupleTableSlot array[1]; /* VARIABLE LENGTH ARRAY - must be last */
} TupleTableData; /* VARIABLE LENGTH STRUCT */
typedef TupleTableData *TupleTable;
/* in access/common/heaptuple.c */
extern Datum slot_getattr(TupleTableSlot *slot, int attnum, bool *isnull);
#endif /* TUPTABLE_H */
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