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Diffstat (limited to 'src/include/access/tsmapi.h')
-rw-r--r-- | src/include/access/tsmapi.h | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/src/include/access/tsmapi.h b/src/include/access/tsmapi.h new file mode 100644 index 0000000..2dc848c --- /dev/null +++ b/src/include/access/tsmapi.h @@ -0,0 +1,82 @@ +/*------------------------------------------------------------------------- + * + * tsmapi.h + * API for tablesample methods + * + * Copyright (c) 2015-2021, 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 */ |