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/*-------------------------------------------------------------------------
*
* tsmapi.h
* API for tablesample methods
*
* Copyright (c) 2015-2020, PostgreSQL Global Development Group
*
* src/include/access/tsmapi.h
*
*-------------------------------------------------------------------------
*/
#ifndef TSMAPI_H
#define TSMAPI_H
#include "nodes/execnodes.h"
#include "nodes/pathnodes.h"
/*
* Callback function signatures --- see tablesample-method.sgml for more info.
*/
typedef void (*SampleScanGetSampleSize_function) (PlannerInfo *root,
RelOptInfo *baserel,
List *paramexprs,
BlockNumber *pages,
double *tuples);
typedef void (*InitSampleScan_function) (SampleScanState *node,
int eflags);
typedef void (*BeginSampleScan_function) (SampleScanState *node,
Datum *params,
int nparams,
uint32 seed);
typedef BlockNumber (*NextSampleBlock_function) (SampleScanState *node,
BlockNumber nblocks);
typedef OffsetNumber (*NextSampleTuple_function) (SampleScanState *node,
BlockNumber blockno,
OffsetNumber maxoffset);
typedef void (*EndSampleScan_function) (SampleScanState *node);
/*
* TsmRoutine is the struct returned by a tablesample method's handler
* function. It provides pointers to the callback functions needed by the
* planner and executor, as well as additional information about the method.
*
* More function pointers are likely to be added in the future.
* Therefore it's recommended that the handler initialize the struct with
* makeNode(TsmRoutine) so that all fields are set to NULL. This will
* ensure that no fields are accidentally left undefined.
*/
typedef struct TsmRoutine
{
NodeTag type;
/* List of datatype OIDs for the arguments of the TABLESAMPLE clause */
List *parameterTypes;
/* Can method produce repeatable samples across, or even within, queries? */
bool repeatable_across_queries;
bool repeatable_across_scans;
/* Functions for planning a SampleScan on a physical table */
SampleScanGetSampleSize_function SampleScanGetSampleSize;
/* Functions for executing a SampleScan on a physical table */
InitSampleScan_function InitSampleScan; /* can be NULL */
BeginSampleScan_function BeginSampleScan;
NextSampleBlock_function NextSampleBlock; /* can be NULL */
NextSampleTuple_function NextSampleTuple;
EndSampleScan_function EndSampleScan; /* can be NULL */
} TsmRoutine;
/* Functions in access/tablesample/tablesample.c */
extern TsmRoutine *GetTsmRoutine(Oid tsmhandler);
#endif /* TSMAPI_H */
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