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/*-------------------------------------------------------------------------
*
* heapam_handler.c
* heap table access method code
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/access/heap/heapam_handler.c
*
*
* NOTES
* This files wires up the lower level heapam.c et routines with the
* tableam abstraction.
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/tableam.h"
#include "storage/bufmgr.h"
#include "utils/builtins.h"
static const TableAmRoutine heapam_methods;
/* ------------------------------------------------------------------------
* Slot related callbacks for heap AM
* ------------------------------------------------------------------------
*/
static const TupleTableSlotOps *
heapam_slot_callbacks(Relation relation)
{
return &TTSOpsBufferHeapTuple;
}
/* ------------------------------------------------------------------------
* Index Scan Callbacks for heap AM
* ------------------------------------------------------------------------
*/
static IndexFetchTableData *
heapam_index_fetch_begin(Relation rel)
{
IndexFetchHeapData *hscan = palloc0(sizeof(IndexFetchHeapData));
hscan->xs_base.rel = rel;
hscan->xs_cbuf = InvalidBuffer;
return &hscan->xs_base;
}
static void
heapam_index_fetch_reset(IndexFetchTableData *scan)
{
IndexFetchHeapData *hscan = (IndexFetchHeapData *) scan;
if (BufferIsValid(hscan->xs_cbuf))
{
ReleaseBuffer(hscan->xs_cbuf);
hscan->xs_cbuf = InvalidBuffer;
}
}
static void
heapam_index_fetch_end(IndexFetchTableData *scan)
{
IndexFetchHeapData *hscan = (IndexFetchHeapData *) scan;
heapam_index_fetch_reset(scan);
pfree(hscan);
}
static bool
heapam_index_fetch_tuple(struct IndexFetchTableData *scan,
ItemPointer tid,
Snapshot snapshot,
TupleTableSlot *slot,
bool *call_again, bool *all_dead)
{
IndexFetchHeapData *hscan = (IndexFetchHeapData *) scan;
BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
bool got_heap_tuple;
Assert(TTS_IS_BUFFERTUPLE(slot));
/* We can skip the buffer-switching logic if we're in mid-HOT chain. */
if (!*call_again)
{
/* Switch to correct buffer if we don't have it already */
Buffer prev_buf = hscan->xs_cbuf;
hscan->xs_cbuf = ReleaseAndReadBuffer(hscan->xs_cbuf,
hscan->xs_base.rel,
ItemPointerGetBlockNumber(tid));
/*
* Prune page, but only if we weren't already on this page
*/
if (prev_buf != hscan->xs_cbuf)
heap_page_prune_opt(hscan->xs_base.rel, hscan->xs_cbuf);
}
/* Obtain share-lock on the buffer so we can examine visibility */
LockBuffer(hscan->xs_cbuf, BUFFER_LOCK_SHARE);
got_heap_tuple = heap_hot_search_buffer(tid,
hscan->xs_base.rel,
hscan->xs_cbuf,
snapshot,
&bslot->base.tupdata,
all_dead,
!*call_again);
bslot->base.tupdata.t_self = *tid;
LockBuffer(hscan->xs_cbuf, BUFFER_LOCK_UNLOCK);
if (got_heap_tuple)
{
/*
* Only in a non-MVCC snapshot can more than one member of the HOT
* chain be visible.
*/
*call_again = !IsMVCCSnapshot(snapshot);
slot->tts_tableOid = RelationGetRelid(scan->rel);
ExecStoreBufferHeapTuple(&bslot->base.tupdata, slot, hscan->xs_cbuf);
}
else
{
/* We've reached the end of the HOT chain. */
*call_again = false;
}
return got_heap_tuple;
}
/* ------------------------------------------------------------------------
* Callbacks for non-modifying operations on individual tuples for heap AM
* ------------------------------------------------------------------------
*/
static bool
heapam_tuple_satisfies_snapshot(Relation rel, TupleTableSlot *slot,
Snapshot snapshot)
{
BufferHeapTupleTableSlot *bslot = (BufferHeapTupleTableSlot *) slot;
bool res;
Assert(TTS_IS_BUFFERTUPLE(slot));
Assert(BufferIsValid(bslot->buffer));
/*
* We need buffer pin and lock to call HeapTupleSatisfiesVisibility.
* Caller should be holding pin, but not lock.
*/
LockBuffer(bslot->buffer, BUFFER_LOCK_SHARE);
res = HeapTupleSatisfiesVisibility(bslot->base.tuple, snapshot,
bslot->buffer);
LockBuffer(bslot->buffer, BUFFER_LOCK_UNLOCK);
return res;
}
/* ------------------------------------------------------------------------
* Definition of the heap table access method.
* ------------------------------------------------------------------------
*/
static const TableAmRoutine heapam_methods = {
.type = T_TableAmRoutine,
.slot_callbacks = heapam_slot_callbacks,
.scan_begin = heap_beginscan,
.scan_end = heap_endscan,
.scan_rescan = heap_rescan,
.scan_getnextslot = heap_getnextslot,
.parallelscan_estimate = table_block_parallelscan_estimate,
.parallelscan_initialize = table_block_parallelscan_initialize,
.parallelscan_reinitialize = table_block_parallelscan_reinitialize,
.index_fetch_begin = heapam_index_fetch_begin,
.index_fetch_reset = heapam_index_fetch_reset,
.index_fetch_end = heapam_index_fetch_end,
.index_fetch_tuple = heapam_index_fetch_tuple,
.tuple_satisfies_snapshot = heapam_tuple_satisfies_snapshot,
};
const TableAmRoutine *
GetHeapamTableAmRoutine(void)
{
return &heapam_methods;
}
Datum
heap_tableam_handler(PG_FUNCTION_ARGS)
{
PG_RETURN_POINTER(&heapam_methods);
}
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