mirror of
https://github.com/timescale/timescaledb.git
synced 2025-05-28 09:46:44 +08:00
1d95dfbe44
This adds an option to set a limit on how many tuples to return in a relation scan using the scanner implemention. This avoids a common pattern of manually implementing limits in the tuple handling function.
88 lines
2.0 KiB
C
88 lines
2.0 KiB
C
#ifndef TIMESCALEDB_SCANNER_H
|
|
#define TIMESCALEDB_SCANNER_H
|
|
|
|
#include <postgres.h>
|
|
#include <access/relscan.h>
|
|
#include <utils/fmgroids.h>
|
|
#include <access/heapam.h>
|
|
#include <nodes/lockoptions.h>
|
|
|
|
typedef enum ScannerType
|
|
{
|
|
ScannerTypeHeap,
|
|
ScannerTypeIndex,
|
|
} ScannerType;
|
|
|
|
/* Tuple information passed on to handlers when scanning for tuples. */
|
|
typedef struct TupleInfo
|
|
{
|
|
Relation scanrel;
|
|
HeapTuple tuple;
|
|
TupleDesc desc;
|
|
/* return index tuple if it was requested -- only for index scans */
|
|
IndexTuple ituple;
|
|
TupleDesc ituple_desc;
|
|
|
|
/*
|
|
* If the user requested a tuple lock, the result of the lock is passed on
|
|
* in lockresult.
|
|
*/
|
|
HTSU_Result lockresult;
|
|
int count;
|
|
} TupleInfo;
|
|
|
|
typedef bool (*tuple_found_func) (TupleInfo *ti, void *data);
|
|
|
|
typedef struct ScannerCtx
|
|
{
|
|
Oid table;
|
|
Oid index;
|
|
ScannerType scantype;
|
|
ScanKey scankey;
|
|
int nkeys,
|
|
norderbys,
|
|
limit; /* Limit on number of tuples to return. 0 or
|
|
* less means no limit */
|
|
bool want_itup;
|
|
LOCKMODE lockmode;
|
|
struct
|
|
{
|
|
LockTupleMode lockmode;
|
|
LockWaitPolicy waitpolicy;
|
|
bool enabled;
|
|
} tuplock;
|
|
ScanDirection scandirection;
|
|
void *data; /* User-provided data passed on to filter()
|
|
* and tuple_found() */
|
|
|
|
/*
|
|
* Optional handler called before a scan starts, but relation locks are
|
|
* acquired.
|
|
*/
|
|
void (*prescan) (void *data);
|
|
|
|
/*
|
|
* Optional handler called after a scan finishes and before relation locks
|
|
* are released. Passes on the number of tuples found.
|
|
*/
|
|
void (*postscan) (int num_tuples, void *data);
|
|
|
|
/*
|
|
* Optional handler to filter tuples. Should return true for tuples that
|
|
* should be passed on to tuple_found, or false otherwise.
|
|
*/
|
|
bool (*filter) (TupleInfo *ti, void *data);
|
|
|
|
/*
|
|
* Handler for found tuples. Should return true to continue the scan or
|
|
* false to abort.
|
|
*/
|
|
bool (*tuple_found) (TupleInfo *ti, void *data);
|
|
} ScannerCtx;
|
|
|
|
/* Performs an index scan or heap scan and returns the number of matching
|
|
* tuples. */
|
|
int scanner_scan(ScannerCtx *ctx);
|
|
|
|
#endif /* TIMESCALEDB_SCANNER_H */
|