OSSForks/postgres
1
0
Fork 0
mirror of https://github.com/zebrajr/postgres.git synced 2025-12-07 00:20:24 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity
c2fe139c20
postgres/src/include/access/heapam.h
Andres Freund c2fe139c20 tableam: Add and use scan APIs. 
Too allow table accesses to be not directly dependent on heap, several
new abstractions are needed. Specifically:

1) Heap scans need to be generalized into table scans. Do this by
   introducing TableScanDesc, which will be the "base class" for
   individual AMs. This contains the AM independent fields from
   HeapScanDesc.

   The previous heap_{beginscan,rescan,endscan} et al. have been
   replaced with a table_ version.

   There's no direct replacement for heap_getnext(), as that returned
   a HeapTuple, which is undesirable for a other AMs. Instead there's
   table_scan_getnextslot().  But note that heap_getnext() lives on,
   it's still used widely to access catalog tables.

   This is achieved by new scan_begin, scan_end, scan_rescan,
   scan_getnextslot callbacks.

2) The portion of parallel scans that's shared between backends need
   to be able to do so without the user doing per-AM work. To achieve
   that new parallelscan_{estimate, initialize, reinitialize}
   callbacks are introduced, which operate on a new
   ParallelTableScanDesc, which again can be subclassed by AMs.

   As it is likely that several AMs are going to be block oriented,
   block oriented callbacks that can be shared between such AMs are
   provided and used by heap. table_block_parallelscan_{estimate,
   intiialize, reinitialize} as callbacks, and
   table_block_parallelscan_{nextpage, init} for use in AMs. These
   operate on a ParallelBlockTableScanDesc.

3) Index scans need to be able to access tables to return a tuple, and
   there needs to be state across individual accesses to the heap to
   store state like buffers. That's now handled by introducing a
   sort-of-scan IndexFetchTable, which again is intended to be
   subclassed by individual AMs (for heap IndexFetchHeap).

   The relevant callbacks for an AM are index_fetch_{end, begin,
   reset} to create the necessary state, and index_fetch_tuple to
   retrieve an indexed tuple.  Note that index_fetch_tuple
   implementations need to be smarter than just blindly fetching the
   tuples for AMs that have optimizations similar to heap's HOT - the
   currently alive tuple in the update chain needs to be fetched if
   appropriate.

   Similar to table_scan_getnextslot(), it's undesirable to continue
   to return HeapTuples. Thus index_fetch_heap (might want to rename
   that later) now accepts a slot as an argument. Core code doesn't
   have a lot of call sites performing index scans without going
   through the systable_* API (in contrast to loads of heap_getnext
   calls and working directly with HeapTuples).

   Index scans now store the result of a search in
   IndexScanDesc->xs_heaptid, rather than xs_ctup->t_self. As the
   target is not generally a HeapTuple anymore that seems cleaner.

To be able to sensible adapt code to use the above, two further
callbacks have been introduced:

a) slot_callbacks returns a TupleTableSlotOps* suitable for creating
   slots capable of holding a tuple of the AMs
   type. table_slot_callbacks() and table_slot_create() are based
   upon that, but have additional logic to deal with views, foreign
   tables, etc.

   While this change could have been done separately, nearly all the
   call sites that needed to be adapted for the rest of this commit
   also would have been needed to be adapted for
   table_slot_callbacks(), making separation not worthwhile.

b) tuple_satisfies_snapshot checks whether the tuple in a slot is
   currently visible according to a snapshot. That's required as a few
   places now don't have a buffer + HeapTuple around, but a
   slot (which in heap's case internally has that information).

Additionally a few infrastructure changes were needed:

I) SysScanDesc, as used by systable_{beginscan, getnext} et al. now
   internally uses a slot to keep track of tuples. While
   systable_getnext() still returns HeapTuples, and will so for the
   foreseeable future, the index API (see 1) above) now only deals with
   slots.

The remainder, and largest part, of this commit is then adjusting all
scans in postgres to use the new APIs.

Author: Andres Freund, Haribabu Kommi, Alvaro Herrera
Discussion:
    https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de
    https://postgr.es/m/20160812231527.GA690404@alvherre.pgsql
2019-03-11 12:46:41 -07:00

248 lines
9.6 KiB
C
Raw Blame History

/*-------------------------------------------------------------------------
*
* heapam.h
* POSTGRES heap access method definitions.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/heapam.h
*
*-------------------------------------------------------------------------
*/
#ifndef HEAPAM_H
#define HEAPAM_H
#include "access/relation.h" /* for backward compatibility */
#include "access/relscan.h"
#include "access/sdir.h"
#include "access/skey.h"
#include "access/table.h" /* for backward compatibility */
#include "nodes/lockoptions.h"
#include "nodes/primnodes.h"
#include "storage/bufpage.h"
#include "storage/lockdefs.h"
#include "utils/relcache.h"
#include "utils/snapshot.h"
/* "options" flag bits for heap_insert */
#define HEAP_INSERT_SKIP_WAL 0x0001
#define HEAP_INSERT_SKIP_FSM 0x0002
#define HEAP_INSERT_FROZEN 0x0004
#define HEAP_INSERT_SPECULATIVE 0x0008
#define HEAP_INSERT_NO_LOGICAL 0x0010
typedef struct BulkInsertStateData *BulkInsertState;
#define MaxLockTupleMode LockTupleExclusive
/*
* When heap_update, heap_delete, or heap_lock_tuple fail because the target
* tuple is already outdated, they fill in this struct to provide information
* to the caller about what happened.
* ctid is the target's ctid link: it is the same as the target's TID if the
* target was deleted, or the location of the replacement tuple if the target
* was updated.
* xmax is the outdating transaction's XID. If the caller wants to visit the
* replacement tuple, it must check that this matches before believing the
* replacement is really a match.
* cmax is the outdating command's CID, but only when the failure code is
* HeapTupleSelfUpdated (i.e., something in the current transaction outdated
* the tuple); otherwise cmax is zero. (We make this restriction because
* HeapTupleHeaderGetCmax doesn't work for tuples outdated in other
* transactions.)
*/
typedef struct HeapUpdateFailureData
{
ItemPointerData ctid;
TransactionId xmax;
CommandId cmax;
} HeapUpdateFailureData;
/*
* Descriptor for heap table scans.
*/
typedef struct HeapScanDescData
{
TableScanDescData rs_base; /* AM independent part of the descriptor */
/* state set up at initscan time */
BlockNumber rs_nblocks; /* total number of blocks in rel */
BlockNumber rs_startblock; /* block # to start at */
BlockNumber rs_numblocks; /* max number of blocks to scan */
/* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
/* scan current state */
bool rs_inited; /* false = scan not init'd yet */
BlockNumber rs_cblock; /* current block # in scan, if any */
Buffer rs_cbuf; /* current buffer in scan, if any */
/* NB: if rs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
/* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
BufferAccessStrategy rs_strategy; /* access strategy for reads */
HeapTupleData rs_ctup; /* current tuple in scan, if any */
/* these fields only used in page-at-a-time mode and for bitmap scans */
int rs_cindex; /* current tuple's index in vistuples */
int rs_ntuples; /* number of visible tuples on page */
OffsetNumber rs_vistuples[MaxHeapTuplesPerPage]; /* their offsets */
} HeapScanDescData;
typedef struct HeapScanDescData *HeapScanDesc;
/*
* Descriptor for fetches from heap via an index.
*/
typedef struct IndexFetchHeapData
{
IndexFetchTableData xs_base; /* AM independent part of the descriptor */
Buffer xs_cbuf; /* current heap buffer in scan, if any */
/* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
} IndexFetchHeapData;
/* Result codes for HeapTupleSatisfiesVacuum */
typedef enum
{
HEAPTUPLE_DEAD, /* tuple is dead and deletable */
HEAPTUPLE_LIVE, /* tuple is live (committed, no deleter) */
HEAPTUPLE_RECENTLY_DEAD, /* tuple is dead, but not deletable yet */
HEAPTUPLE_INSERT_IN_PROGRESS, /* inserting xact is still in progress */
HEAPTUPLE_DELETE_IN_PROGRESS /* deleting xact is still in progress */
} HTSV_Result;
/* ----------------
* function prototypes for heap access method
*
* heap_create, heap_create_with_catalog, and heap_drop_with_catalog
* are declared in catalog/heap.h
* ----------------
*/
/*
* HeapScanIsValid
* True iff the heap scan is valid.
*/
#define HeapScanIsValid(scan) PointerIsValid(scan)
extern TableScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key,
ParallelTableScanDesc parallel_scan,
bool allow_strat,
bool allow_sync,
bool allow_pagemode,
bool is_bitmapscan,
bool is_samplescan,
bool temp_snap);
extern void heap_setscanlimits(TableScanDesc scan, BlockNumber startBlk,
BlockNumber endBlk);
extern void heapgetpage(TableScanDesc scan, BlockNumber page);
extern void heap_rescan(TableScanDesc scan, ScanKey key, bool set_params,
bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_rescan_set_params(TableScanDesc scan, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_endscan(TableScanDesc scan);
extern HeapTuple heap_getnext(TableScanDesc scan, ScanDirection direction);
extern bool heap_getnextslot(TableScanDesc sscan,
ScanDirection direction, struct TupleTableSlot *slot);
extern bool heap_fetch(Relation relation, Snapshot snapshot,
HeapTuple tuple, Buffer *userbuf, bool keep_buf,
Relation stats_relation);
extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation,
Buffer buffer, Snapshot snapshot, HeapTuple heapTuple,
bool *all_dead, bool first_call);
extern bool heap_hot_search(ItemPointer tid, Relation relation,
Snapshot snapshot, bool *all_dead);
extern void heap_get_latest_tid(Relation relation, Snapshot snapshot,
ItemPointer tid);
extern void setLastTid(const ItemPointer tid);
extern BulkInsertState GetBulkInsertState(void);
extern void FreeBulkInsertState(BulkInsertState);
extern void ReleaseBulkInsertStatePin(BulkInsertState bistate);
extern void heap_insert(Relation relation, HeapTuple tup, CommandId cid,
int options, BulkInsertState bistate);
extern void heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
CommandId cid, int options, BulkInsertState bistate);
extern HTSU_Result heap_delete(Relation relation, ItemPointer tid,
CommandId cid, Snapshot crosscheck, bool wait,
HeapUpdateFailureData *hufd, bool changingPart);
extern void heap_finish_speculative(Relation relation, HeapTuple tuple);
extern void heap_abort_speculative(Relation relation, HeapTuple tuple);
extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
HeapTuple newtup,
CommandId cid, Snapshot crosscheck, bool wait,
HeapUpdateFailureData *hufd, LockTupleMode *lockmode);
extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
bool follow_update,
Buffer *buffer, HeapUpdateFailureData *hufd);
extern void heap_inplace_update(Relation relation, HeapTuple tuple);
extern bool heap_freeze_tuple(HeapTupleHeader tuple,
TransactionId relfrozenxid, TransactionId relminmxid,
TransactionId cutoff_xid, TransactionId cutoff_multi);
extern bool heap_tuple_needs_freeze(HeapTupleHeader tuple, TransactionId cutoff_xid,
MultiXactId cutoff_multi, Buffer buf);
extern bool heap_tuple_needs_eventual_freeze(HeapTupleHeader tuple);
extern void simple_heap_insert(Relation relation, HeapTuple tup);
extern void simple_heap_delete(Relation relation, ItemPointer tid);
extern void simple_heap_update(Relation relation, ItemPointer otid,
HeapTuple tup);
extern void heap_sync(Relation relation);
/* in heap/pruneheap.c */
extern void heap_page_prune_opt(Relation relation, Buffer buffer);
extern int heap_page_prune(Relation relation, Buffer buffer,
TransactionId OldestXmin,
bool report_stats, TransactionId *latestRemovedXid);
extern void heap_page_prune_execute(Buffer buffer,
OffsetNumber *redirected, int nredirected,
OffsetNumber *nowdead, int ndead,
OffsetNumber *nowunused, int nunused);
extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
/* in heap/syncscan.c */
extern void ss_report_location(Relation rel, BlockNumber location);
extern BlockNumber ss_get_location(Relation rel, BlockNumber relnblocks);
extern void SyncScanShmemInit(void);
extern Size SyncScanShmemSize(void);
/* in heap/vacuumlazy.c */
struct VacuumParams;
extern void heap_vacuum_rel(Relation onerel, int options,
struct VacuumParams *params, BufferAccessStrategy bstrategy);
/* in heap/heapam_visibility.c */
extern bool HeapTupleSatisfiesVisibility(HeapTuple stup, Snapshot snapshot,
Buffer buffer);
extern HTSU_Result HeapTupleSatisfiesUpdate(HeapTuple stup, CommandId curcid,
Buffer buffer);
extern HTSV_Result HeapTupleSatisfiesVacuum(HeapTuple stup, TransactionId OldestXmin,
Buffer buffer);
extern void HeapTupleSetHintBits(HeapTupleHeader tuple, Buffer buffer,
uint16 infomask, TransactionId xid);
extern bool HeapTupleHeaderIsOnlyLocked(HeapTupleHeader tuple);
extern bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot);
extern bool HeapTupleIsSurelyDead(HeapTuple htup, TransactionId OldestXmin);
/*
* To avoid leaking too much knowledge about reorderbuffer implementation
* details this is implemented in reorderbuffer.c not heapam_visibility.c
*/
struct HTAB;
extern bool ResolveCminCmaxDuringDecoding(struct HTAB *tuplecid_data,
Snapshot snapshot,
HeapTuple htup,
Buffer buffer,
CommandId *cmin, CommandId *cmax);
#endif /* HEAPAM_H */
Reference in New Issue View Git Blame Copy Permalink