src/tutorial/funcs_new.c

   1 /* $PostgreSQL$ */
   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
  20 PG_MODULE_MAGIC;
  21
  22 /* These prototypes just prevent possible warnings from gcc. */
  23
  24 Datum           add_one(PG_FUNCTION_ARGS);
  25 Datum           add_one_float8(PG_FUNCTION_ARGS);
  26 Datum           makepoint(PG_FUNCTION_ARGS);
  27 Datum           copytext(PG_FUNCTION_ARGS);
  28 Datum           concat_text(PG_FUNCTION_ARGS);
  29 Datum           c_overpaid(PG_FUNCTION_ARGS);
  30
  31
  32 /* By Value */
  33
  34 PG_FUNCTION_INFO_V1(add_one);
  35
  36 Datum
  37 add_one(PG_FUNCTION_ARGS)
  38 {
  39         int32           arg = PG_GETARG_INT32(0);
  40
  41         PG_RETURN_INT32(arg + 1);
  42 }
  43
  44 /* By Reference, Fixed Length */
  45
  46 PG_FUNCTION_INFO_V1(add_one_float8);
  47
  48 Datum
  49 add_one_float8(PG_FUNCTION_ARGS)
  50 {
  51         /* The macros for FLOAT8 hide its pass-by-reference nature */
  52         float8          arg = PG_GETARG_FLOAT8(0);
  53
  54         PG_RETURN_FLOAT8(arg + 1.0);
  55 }
  56
  57 PG_FUNCTION_INFO_V1(makepoint);
  58
  59 Datum
  60 makepoint(PG_FUNCTION_ARGS)
  61 {
  62         Point      *pointx = PG_GETARG_POINT_P(0);
  63         Point      *pointy = PG_GETARG_POINT_P(1);
  64         Point      *new_point = (Point *) palloc(sizeof(Point));
  65
  66         new_point->x = pointx->x;
  67         new_point->y = pointy->y;
  68
  69         PG_RETURN_POINT_P(new_point);
  70 }
  71
  72 /* By Reference, Variable Length */
  73
  74 PG_FUNCTION_INFO_V1(copytext);
  75
  76 Datum
  77 copytext(PG_FUNCTION_ARGS)
  78 {
  79         text       *t = PG_GETARG_TEXT_P(0);
  80
  81         /*
  82          * VARSIZE is the total size of the struct in bytes.
  83          */
  84         text       *new_t = (text *) palloc(VARSIZE(t));
  85
  86         SET_VARSIZE(new_t, VARSIZE(t));
  87
  88         /*
  89          * VARDATA is a pointer to the data region of the struct.
  90          */
  91         memcpy((void *) VARDATA(new_t),         /* destination */
  92                    (void *) VARDATA(t), /* source */
  93                    VARSIZE(t) - VARHDRSZ);              /* how many bytes */
  94         PG_RETURN_TEXT_P(new_t);
  95 }
  96
  97 PG_FUNCTION_INFO_V1(concat_text);
  98
  99 Datum
 100 concat_text(PG_FUNCTION_ARGS)
 101 {
 102         text       *arg1 = PG_GETARG_TEXT_P(0);
 103         text       *arg2 = PG_GETARG_TEXT_P(1);
 104         int32           arg1_size = VARSIZE(arg1) - VARHDRSZ;
 105         int32           arg2_size = VARSIZE(arg2) - VARHDRSZ;
 106         int32           new_text_size = arg1_size + arg2_size + VARHDRSZ;
 107         text       *new_text = (text *) palloc(new_text_size);
 108
 109         SET_VARSIZE(new_text, new_text_size);
 110         memcpy(VARDATA(new_text), VARDATA(arg1), arg1_size);
 111         memcpy(VARDATA(new_text) + arg1_size, VARDATA(arg2), arg2_size);
 112         PG_RETURN_TEXT_P(new_text);
 113 }
 114
 115 /* Composite types */
 116
 117 PG_FUNCTION_INFO_V1(c_overpaid);
 118
 119 Datum
 120 c_overpaid(PG_FUNCTION_ARGS)
 121 {
 122         HeapTupleHeader t = PG_GETARG_HEAPTUPLEHEADER(0);
 123         int32           limit = PG_GETARG_INT32(1);
 124         bool            isnull;
 125         int32           salary;
 126
 127         salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
 128         if (isnull)
 129                 PG_RETURN_BOOL(false);
 130
 131         /*
 132          * Alternatively, we might prefer to do PG_RETURN_NULL() for null salary
 133          */
 134
 135         PG_RETURN_BOOL(salary > limit);
 136 }