src/include/access/attmap.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * attmap.h
   4  *        Definitions for PostgreSQL attribute mappings
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * src/include/access/attmap.h
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef ATTMAP_H
  15 #define ATTMAP_H
  16
  17 #include "access/attnum.h"
  18 #include "access/tupdesc.h"
  19
  20 /*
  21  * Attribute mapping structure
  22  *
  23  * This maps attribute numbers between a pair of relations, designated
  24  * 'input' and 'output' (most typically inheritance parent and child
  25  * relations), whose common columns may have different attribute numbers.
  26  * Such difference may arise due to the columns being ordered differently
  27  * in the two relations or the two relations having dropped columns at
  28  * different positions.
  29  *
  30  * 'maplen' is set to the number of attributes of the 'output' relation,
  31  * taking into account any of its dropped attributes, with the corresponding
  32  * elements of the 'attnums' array set to 0.
  33  */
  34 typedef struct AttrMap
  35 {
  36         AttrNumber *attnums;
  37         int                     maplen;
  38 } AttrMap;
  39
  40 extern AttrMap *make_attrmap(int maplen);
  41 extern void free_attrmap(AttrMap *map);
  42
  43 /* Conversion routines to build mappings */
  44 extern AttrMap *build_attrmap_by_name(TupleDesc indesc,
  45                                                                           TupleDesc outdesc);
  46 extern AttrMap *build_attrmap_by_name_if_req(TupleDesc indesc,
  47                                                                                          TupleDesc outdesc);
  48 extern AttrMap *build_attrmap_by_position(TupleDesc indesc,
  49                                                                                   TupleDesc outdesc,
  50                                                                                   const char *msg);
  51
  52 #endif                                                  /* ATTMAP_H */