83 lines
2.6 KiB
C
83 lines
2.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* tsmapi.h
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* API for tablesample methods
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*
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* Copyright (c) 2015-2023, PostgreSQL Global Development Group
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*
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* src/include/access/tsmapi.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef TSMAPI_H
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#define TSMAPI_H
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#include "nodes/execnodes.h"
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#include "nodes/pathnodes.h"
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/*
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* Callback function signatures --- see tablesample-method.sgml for more info.
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*/
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typedef void (*SampleScanGetSampleSize_function) (PlannerInfo *root,
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RelOptInfo *baserel,
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List *paramexprs,
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BlockNumber *pages,
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double *tuples);
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typedef void (*InitSampleScan_function) (SampleScanState *node,
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int eflags);
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typedef void (*BeginSampleScan_function) (SampleScanState *node,
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Datum *params,
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int nparams,
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uint32 seed);
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typedef BlockNumber (*NextSampleBlock_function) (SampleScanState *node,
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BlockNumber nblocks);
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typedef OffsetNumber (*NextSampleTuple_function) (SampleScanState *node,
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BlockNumber blockno,
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OffsetNumber maxoffset);
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typedef void (*EndSampleScan_function) (SampleScanState *node);
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/*
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* TsmRoutine is the struct returned by a tablesample method's handler
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* function. It provides pointers to the callback functions needed by the
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* planner and executor, as well as additional information about the method.
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*
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* More function pointers are likely to be added in the future.
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* Therefore it's recommended that the handler initialize the struct with
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* makeNode(TsmRoutine) so that all fields are set to NULL. This will
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* ensure that no fields are accidentally left undefined.
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*/
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typedef struct TsmRoutine
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{
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NodeTag type;
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/* List of datatype OIDs for the arguments of the TABLESAMPLE clause */
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List *parameterTypes;
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/* Can method produce repeatable samples across, or even within, queries? */
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bool repeatable_across_queries;
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bool repeatable_across_scans;
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/* Functions for planning a SampleScan on a physical table */
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SampleScanGetSampleSize_function SampleScanGetSampleSize;
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/* Functions for executing a SampleScan on a physical table */
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InitSampleScan_function InitSampleScan; /* can be NULL */
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BeginSampleScan_function BeginSampleScan;
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NextSampleBlock_function NextSampleBlock; /* can be NULL */
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NextSampleTuple_function NextSampleTuple;
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EndSampleScan_function EndSampleScan; /* can be NULL */
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} TsmRoutine;
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/* Functions in access/tablesample/tablesample.c */
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extern TsmRoutine *GetTsmRoutine(Oid tsmhandler);
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#endif /* TSMAPI_H */
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