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/*-------------------------------------------------------------------------
*
* attmap.h
* Definitions for PostgreSQL attribute mappings
*
*
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/attmap.h
*
*-------------------------------------------------------------------------
*/
#ifndef ATTMAP_H
#define ATTMAP_H
#include "access/attnum.h"
#include "access/tupdesc.h"
/*
* Attribute mapping structure
*
* This maps attribute numbers between a pair of relations, designated
* 'input' and 'output' (most typically inheritance parent and child
* relations), whose common columns may have different attribute numbers.
* Such difference may arise due to the columns being ordered differently
* in the two relations or the two relations having dropped columns at
* different positions.
*
* 'maplen' is set to the number of attributes of the 'output' relation,
* taking into account any of its dropped attributes, with the corresponding
* elements of the 'attnums' array set to 0.
*/
typedef struct AttrMap
{
AttrNumber *attnums;
int maplen;
} AttrMap;
extern AttrMap *make_attrmap(int maplen);
extern void free_attrmap(AttrMap *map);
/* Conversion routines to build mappings */
extern AttrMap *build_attrmap_by_name(TupleDesc indesc,
TupleDesc outdesc);
extern AttrMap *build_attrmap_by_name_if_req(TupleDesc indesc,
TupleDesc outdesc);
extern AttrMap *build_attrmap_by_position(TupleDesc indesc,
TupleDesc outdesc,
const char *msg);
#endif /* ATTMAP_H */
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