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) 1996-2021, 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 * Serialize and restore datums so that we can transfer them to parallel 60 * workers. 61 */ 62 extern Size datumEstimateSpace(Datum value, bool isnull, bool typByVal, 63 int typLen); 64 extern void datumSerialize(Datum value, bool isnull, bool typByVal, 65 int typLen, char **start_address); 66 extern Datum datumRestore(char **start_address, bool *isnull); 67 68 #endif /* DATUM_H */ 69