tuplestore.h

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/*-------------------------------------------------------------------------
 *
 * tuplestore.h
 *    Generalized routines for temporary tuple storage.
 *
 * This module handles temporary storage of tuples for purposes such
 * as Materialize nodes, hashjoin batch files, etc.  It is essentially
 * a dumbed-down version of tuplesort.c; it does no sorting of tuples
 * but can only store and regurgitate a sequence of tuples.  However,
 * because no sort is required, it is allowed to start reading the sequence
 * before it has all been written.  This is particularly useful for cursors,
 * because it allows random access within the already-scanned portion of
 * a query without having to process the underlying scan to completion.
 * Also, it is possible to support multiple independent read pointers.
 *
 * A temporary file is used to handle the data if it exceeds the
 * space limit specified by the caller.
 *
 * Beginning in Postgres 8.2, what is stored is just MinimalTuples;
 * callers cannot expect valid system columns in regurgitated tuples.
 * Also, we have changed the API to return tuples in TupleTableSlots,
 * so that there is a check to prevent attempted access to system columns.
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/tuplestore.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef TUPLESTORE_H
#define TUPLESTORE_H

#include "executor/tuptable.h"


/* Tuplestorestate is an opaque type whose details are not known outside
 * tuplestore.c.
 */
typedef struct Tuplestorestate Tuplestorestate;

/*
 * Currently we only need to store MinimalTuples, but it would be easy
 * to support the same behavior for IndexTuples and/or bare Datums.
 */

extern Tuplestorestate *tuplestore_begin_heap(bool randomAccess,
                      bool interXact,
                      int maxKBytes);

extern void tuplestore_set_eflags(Tuplestorestate *state, int eflags);

extern void tuplestore_puttupleslot(Tuplestorestate *state,
                        TupleTableSlot *slot);
extern void tuplestore_puttuple(Tuplestorestate *state, HeapTuple tuple);
extern void tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc,
                     Datum *values, bool *isnull);

/* tuplestore_donestoring() used to be required, but is no longer used */
#define tuplestore_donestoring(state)   ((void) 0)

extern int  tuplestore_alloc_read_pointer(Tuplestorestate *state, int eflags);

extern void tuplestore_select_read_pointer(Tuplestorestate *state, int ptr);

extern void tuplestore_copy_read_pointer(Tuplestorestate *state,
                             int srcptr, int destptr);

extern void tuplestore_trim(Tuplestorestate *state);

extern bool tuplestore_in_memory(Tuplestorestate *state);

extern bool tuplestore_gettupleslot(Tuplestorestate *state, bool forward,
                        bool copy, TupleTableSlot *slot);
extern bool tuplestore_advance(Tuplestorestate *state, bool forward);

extern bool tuplestore_ateof(Tuplestorestate *state);

extern void tuplestore_rescan(Tuplestorestate *state);

extern void tuplestore_clear(Tuplestorestate *state);

extern void tuplestore_end(Tuplestorestate *state);

#endif   /* TUPLESTORE_H */