src/include/utils/datum.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * datum.h
   4  *        POSTGRES Datum (abstract data type) manipulation routines.
   5  *
   6  * These routines are driven by the 'typbyval' and 'typlen' information,
   7  * which must previously have been obtained by the caller for the datatype
   8  * of the Datum.  (We do it this way because in most situations the caller
   9  * can look up the info just once and use it for many per-datum operations.)
  10  *
  11  * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
  12  * Portions Copyright (c) 1994, Regents of the University of California
  13  *
  14  * src/include/utils/datum.h
  15  *
  16  *-------------------------------------------------------------------------
  17  */
  18 #ifndef DATUM_H
  19 #define DATUM_H
  20
  21 /*
  22  * datumGetSize - find the "real" length of a datum
  23  */
  24 extern Size datumGetSize(Datum value, bool typByVal, int typLen);
  25
  26 /*
  27  * datumCopy - make a copy of a non-NULL datum.
  28  *
  29  * If the datatype is pass-by-reference, memory is obtained with palloc().
  30  */
  31 extern Datum datumCopy(Datum value, bool typByVal, int typLen);
  32
  33 /*
  34  * datumTransfer - transfer a non-NULL datum into the current memory context.
  35  *
  36  * Differs from datumCopy() in its handling of read-write expanded objects.
  37  */
  38 extern Datum datumTransfer(Datum value, bool typByVal, int typLen);
  39
  40 /*
  41  * datumIsEqual
  42  * return true if two datums of the same type are equal, false otherwise.
  43  *
  44  * XXX : See comments in the code for restrictions!
  45  */
  46 extern bool datumIsEqual(Datum value1, Datum value2,
  47                                                  bool typByVal, int typLen);
  48
  49 /*
  50  * datum_image_eq
  51  *
  52  * Compares two datums for identical contents, based on byte images.  Return
  53  * true if the two datums are equal, false otherwise.
  54  */
  55 extern bool datum_image_eq(Datum value1, Datum value2,
  56                                                    bool typByVal, int typLen);
  57
  58 /*
  59  * datum_image_hash
  60  *
  61  * Generates hash value for 'value' based on its bits rather than logical
  62  * value.
  63  */
  64 extern uint32 datum_image_hash(Datum value, bool typByVal, int typLen);
  65
  66 /*
  67  * Serialize and restore datums so that we can transfer them to parallel
  68  * workers.
  69  */
  70 extern Size datumEstimateSpace(Datum value, bool isnull, bool typByVal,
  71                                                            int typLen);
  72 extern void datumSerialize(Datum value, bool isnull, bool typByVal,
  73                                                    int typLen, char **start_address);
  74 extern Datum datumRestore(char **start_address, bool *isnull);
  75
  76 #endif                                                  /* DATUM_H */