granicus.if.org Git - postgresql/blob - src/tutorial/funcs_new.c

   1 /* src/tutorial/funcs_new.c */
   2
   3 /******************************************************************************
   4   These are user-defined functions that can be bound to a Postgres backend
   5   and called by Postgres to execute SQL functions of the same name.
   6
   7   The calling format for these functions is defined by the CREATE FUNCTION
   8   SQL statement that binds them to the backend.
   9
  10   NOTE: this file shows examples of "new style" function call conventions.
  11   See funcs.c for examples of "old style".
  12 *****************************************************************************/
  13
  14 #include "postgres.h"                   /* general Postgres declarations */
  15
  16 #include "executor/executor.h"  /* for GetAttributeByName() */
  17 #include "utils/geo_decls.h"    /* for point type */
  18
  19 PG_MODULE_MAGIC;
  20
  21
  22 /* By Value */
  23
  24 PG_FUNCTION_INFO_V1(add_one);
  25
  26 Datum
  27 add_one(PG_FUNCTION_ARGS)
  28 {
  29         int32           arg = PG_GETARG_INT32(0);
  30
  31         PG_RETURN_INT32(arg + 1);
  32 }
  33
  34 /* By Reference, Fixed Length */
  35
  36 PG_FUNCTION_INFO_V1(add_one_float8);
  37
  38 Datum
  39 add_one_float8(PG_FUNCTION_ARGS)
  40 {
  41         /* The macros for FLOAT8 hide its pass-by-reference nature */
  42         float8          arg = PG_GETARG_FLOAT8(0);
  43
  44         PG_RETURN_FLOAT8(arg + 1.0);
  45 }
  46
  47 PG_FUNCTION_INFO_V1(makepoint);
  48
  49 Datum
  50 makepoint(PG_FUNCTION_ARGS)
  51 {
  52         Point      *pointx = PG_GETARG_POINT_P(0);
  53         Point      *pointy = PG_GETARG_POINT_P(1);
  54         Point      *new_point = (Point *) palloc(sizeof(Point));
  55
  56         new_point->x = pointx->x;
  57         new_point->y = pointy->y;
  58
  59         PG_RETURN_POINT_P(new_point);
  60 }
  61
  62 /* By Reference, Variable Length */
  63
  64 PG_FUNCTION_INFO_V1(copytext);
  65
  66 Datum
  67 copytext(PG_FUNCTION_ARGS)
  68 {
  69         text       *t = PG_GETARG_TEXT_P(0);
  70
  71         /*
  72          * VARSIZE is the total size of the struct in bytes.
  73          */
  74         text       *new_t = (text *) palloc(VARSIZE(t));
  75
  76         SET_VARSIZE(new_t, VARSIZE(t));
  77
  78         /*
  79          * VARDATA is a pointer to the data region of the struct.
  80          */
  81         memcpy((void *) VARDATA(new_t),         /* destination */
  82                    (void *) VARDATA(t), /* source */
  83                    VARSIZE(t) - VARHDRSZ);              /* how many bytes */
  84         PG_RETURN_TEXT_P(new_t);
  85 }
  86
  87 PG_FUNCTION_INFO_V1(concat_text);
  88
  89 Datum
  90 concat_text(PG_FUNCTION_ARGS)
  91 {
  92         text       *arg1 = PG_GETARG_TEXT_P(0);
  93         text       *arg2 = PG_GETARG_TEXT_P(1);
  94         int32           arg1_size = VARSIZE(arg1) - VARHDRSZ;
  95         int32           arg2_size = VARSIZE(arg2) - VARHDRSZ;
  96         int32           new_text_size = arg1_size + arg2_size + VARHDRSZ;
  97         text       *new_text = (text *) palloc(new_text_size);
  98
  99         SET_VARSIZE(new_text, new_text_size);
 100         memcpy(VARDATA(new_text), VARDATA(arg1), arg1_size);
 101         memcpy(VARDATA(new_text) + arg1_size, VARDATA(arg2), arg2_size);
 102         PG_RETURN_TEXT_P(new_text);
 103 }
 104
 105 /* Composite types */
 106
 107 PG_FUNCTION_INFO_V1(c_overpaid);
 108
 109 Datum
 110 c_overpaid(PG_FUNCTION_ARGS)
 111 {
 112         HeapTupleHeader t = PG_GETARG_HEAPTUPLEHEADER(0);
 113         int32           limit = PG_GETARG_INT32(1);
 114         bool            isnull;
 115         int32           salary;
 116
 117         salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
 118         if (isnull)
 119                 PG_RETURN_BOOL(false);
 120
 121         /*
 122          * Alternatively, we might prefer to do PG_RETURN_NULL() for null salary
 123          */
 124
 125         PG_RETURN_BOOL(salary > limit);
 126 }