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162 lines
6.4 KiB
C
162 lines
6.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* relscan.h
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* POSTGRES relation scan descriptor definitions.
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*
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/relscan.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef RELSCAN_H
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#define RELSCAN_H
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#include "access/genam.h"
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#include "access/heapam.h"
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#include "access/htup_details.h"
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#include "access/itup.h"
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#include "access/tupdesc.h"
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#include "storage/spin.h"
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/*
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* Shared state for parallel heap scan.
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*
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* Each backend participating in a parallel heap scan has its own
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* HeapScanDesc in backend-private memory, and those objects all contain
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* a pointer to this structure. The information here must be sufficient
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* to properly initialize each new HeapScanDesc as workers join the scan,
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* and it must act as a font of block numbers for those workers.
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*/
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typedef struct ParallelHeapScanDescData
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{
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Oid phs_relid; /* OID of relation to scan */
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bool phs_syncscan; /* report location to syncscan logic? */
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BlockNumber phs_nblocks; /* # blocks in relation at start of scan */
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slock_t phs_mutex; /* mutual exclusion for block number fields */
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BlockNumber phs_startblock; /* starting block number */
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BlockNumber phs_cblock; /* current block number */
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char phs_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
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} ParallelHeapScanDescData;
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typedef struct HeapScanDescData
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{
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/* scan parameters */
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Relation rs_rd; /* heap relation descriptor */
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Snapshot rs_snapshot; /* snapshot to see */
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int rs_nkeys; /* number of scan keys */
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ScanKey rs_key; /* array of scan key descriptors */
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bool rs_bitmapscan; /* true if this is really a bitmap scan */
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bool rs_samplescan; /* true if this is really a sample scan */
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bool rs_pageatatime; /* verify visibility page-at-a-time? */
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bool rs_allow_strat; /* allow or disallow use of access strategy */
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bool rs_allow_sync; /* allow or disallow use of syncscan */
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bool rs_temp_snap; /* unregister snapshot at scan end? */
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/* state set up at initscan time */
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BlockNumber rs_nblocks; /* total number of blocks in rel */
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BlockNumber rs_startblock; /* block # to start at */
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BlockNumber rs_numblocks; /* max number of blocks to scan */
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/* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
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BufferAccessStrategy rs_strategy; /* access strategy for reads */
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bool rs_syncscan; /* report location to syncscan logic? */
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/* scan current state */
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bool rs_inited; /* false = scan not init'd yet */
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HeapTupleData rs_ctup; /* current tuple in scan, if any */
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BlockNumber rs_cblock; /* current block # in scan, if any */
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Buffer rs_cbuf; /* current buffer in scan, if any */
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/* NB: if rs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
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ParallelHeapScanDesc rs_parallel; /* parallel scan information */
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/* these fields only used in page-at-a-time mode and for bitmap scans */
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int rs_cindex; /* current tuple's index in vistuples */
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int rs_ntuples; /* number of visible tuples on page */
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OffsetNumber rs_vistuples[MaxHeapTuplesPerPage]; /* their offsets */
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} HeapScanDescData;
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/*
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* We use the same IndexScanDescData structure for both amgettuple-based
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* and amgetbitmap-based index scans. Some fields are only relevant in
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* amgettuple-based scans.
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*/
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typedef struct IndexScanDescData
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{
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/* scan parameters */
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Relation heapRelation; /* heap relation descriptor, or NULL */
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Relation indexRelation; /* index relation descriptor */
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Snapshot xs_snapshot; /* snapshot to see */
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int numberOfKeys; /* number of index qualifier conditions */
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int numberOfOrderBys; /* number of ordering operators */
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ScanKey keyData; /* array of index qualifier descriptors */
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ScanKey orderByData; /* array of ordering op descriptors */
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bool xs_want_itup; /* caller requests index tuples */
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bool xs_temp_snap; /* unregister snapshot at scan end? */
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/* signaling to index AM about killing index tuples */
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bool kill_prior_tuple; /* last-returned tuple is dead */
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bool ignore_killed_tuples; /* do not return killed entries */
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bool xactStartedInRecovery; /* prevents killing/seeing killed
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* tuples */
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/* index access method's private state */
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void *opaque; /* access-method-specific info */
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/*
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* In an index-only scan, a successful amgettuple call must fill either
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* xs_itup (and xs_itupdesc) or xs_hitup (and xs_hitupdesc) to provide the
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* data returned by the scan. It can fill both, in which case the heap
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* format will be used.
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*/
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IndexTuple xs_itup; /* index tuple returned by AM */
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TupleDesc xs_itupdesc; /* rowtype descriptor of xs_itup */
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HeapTuple xs_hitup; /* index data returned by AM, as HeapTuple */
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TupleDesc xs_hitupdesc; /* rowtype descriptor of xs_hitup */
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/* xs_ctup/xs_cbuf/xs_recheck are valid after a successful index_getnext */
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HeapTupleData xs_ctup; /* current heap tuple, if any */
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Buffer xs_cbuf; /* current heap buffer in scan, if any */
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/* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
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bool xs_recheck; /* T means scan keys must be rechecked */
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/*
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* When fetching with an ordering operator, the values of the ORDER BY
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* expressions of the last returned tuple, according to the index. If
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* xs_recheckorderby is true, these need to be rechecked just like the
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* scan keys, and the values returned here are a lower-bound on the actual
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* values.
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*/
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Datum *xs_orderbyvals;
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bool *xs_orderbynulls;
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bool xs_recheckorderby;
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/* state data for traversing HOT chains in index_getnext */
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bool xs_continue_hot; /* T if must keep walking HOT chain */
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/* parallel index scan information, in shared memory */
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ParallelIndexScanDesc parallel_scan;
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} IndexScanDescData;
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/* Generic structure for parallel scans */
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typedef struct ParallelIndexScanDescData
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{
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Oid ps_relid;
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Oid ps_indexid;
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Size ps_offset; /* Offset in bytes of am specific structure */
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char ps_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
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} ParallelIndexScanDescData;
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/* Struct for heap-or-index scans of system tables */
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typedef struct SysScanDescData
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{
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Relation heap_rel; /* catalog being scanned */
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Relation irel; /* NULL if doing heap scan */
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HeapScanDesc scan; /* only valid in heap-scan case */
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IndexScanDesc iscan; /* only valid in index-scan case */
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Snapshot snapshot; /* snapshot to unregister at end of scan */
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} SysScanDescData;
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#endif /* RELSCAN_H */
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