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

   1 /******************************************************************************
   2   These are user-defined functions that can be bound to a Postgres backend
   3   and called by Postgres to execute SQL functions of the same name.
   4
   5   The calling format for these functions is defined by the CREATE FUNCTION
   6   SQL statement that binds them to the backend.
   7
   8   NOTE: this file shows examples of "new style" function call conventions.
   9   See funcs.c for examples of "old style".
  10 *****************************************************************************/
  11
  12 #include "postgres.h"                   /* general Postgres declarations */
  13
  14 #include "fmgr.h"                               /* for argument/result macros */
  15 #include "executor/executor.h"  /* for GetAttributeByName() */
  16 #include "utils/geo_decls.h"    /* for point type */
  17
  18
  19 /* These prototypes just prevent possible warnings from gcc. */
  20
  21 Datum           add_one(PG_FUNCTION_ARGS);
  22 Datum           add_one_float8(PG_FUNCTION_ARGS);
  23 Datum           makepoint(PG_FUNCTION_ARGS);
  24 Datum           copytext(PG_FUNCTION_ARGS);
  25 Datum           concat_text(PG_FUNCTION_ARGS);
  26 Datum           c_overpaid(PG_FUNCTION_ARGS);
  27
  28
  29 /* By Value */
  30
  31 PG_FUNCTION_INFO_V1(add_one);
  32
  33 Datum
  34 add_one(PG_FUNCTION_ARGS)
  35 {
  36         int32           arg = PG_GETARG_INT32(0);
  37
  38         PG_RETURN_INT32(arg + 1);
  39 }
  40
  41 /* By Reference, Fixed Length */
  42
  43 PG_FUNCTION_INFO_V1(add_one_float8);
  44
  45 Datum
  46 add_one_float8(PG_FUNCTION_ARGS)
  47 {
  48         /* The macros for FLOAT8 hide its pass-by-reference nature */
  49         float8          arg = PG_GETARG_FLOAT8(0);
  50
  51         PG_RETURN_FLOAT8(arg + 1.0);
  52 }
  53
  54 PG_FUNCTION_INFO_V1(makepoint);
  55
  56 Datum
  57 makepoint(PG_FUNCTION_ARGS)
  58 {
  59         Point      *pointx = PG_GETARG_POINT_P(0);
  60         Point      *pointy = PG_GETARG_POINT_P(1);
  61         Point      *new_point = (Point *) palloc(sizeof(Point));
  62
  63         new_point->x = pointx->x;
  64         new_point->y = pointy->y;
  65
  66         PG_RETURN_POINT_P(new_point);
  67 }
  68
  69 /* By Reference, Variable Length */
  70
  71 PG_FUNCTION_INFO_V1(copytext);
  72
  73 Datum
  74 copytext(PG_FUNCTION_ARGS)
  75 {
  76         text       *t = PG_GETARG_TEXT_P(0);
  77
  78         /*
  79          * VARSIZE is the total size of the struct in bytes.
  80          */
  81         text       *new_t = (text *) palloc(VARSIZE(t));
  82
  83         VARATT_SIZEP(new_t) = VARSIZE(t);
  84
  85         /*
  86          * VARDATA is a pointer to the data region of the struct.
  87          */
  88         memcpy((void *) VARDATA(new_t),         /* destination */
  89                    (void *) VARDATA(t), /* source */
  90                    VARSIZE(t) - VARHDRSZ);              /* how many bytes */
  91         PG_RETURN_TEXT_P(new_t);
  92 }
  93
  94 PG_FUNCTION_INFO_V1(concat_text);
  95
  96 Datum
  97 concat_text(PG_FUNCTION_ARGS)
  98 {
  99         text       *arg1 = PG_GETARG_TEXT_P(0);
 100         text       *arg2 = PG_GETARG_TEXT_P(1);
 101         int32           new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ;
 102         text       *new_text = (text *) palloc(new_text_size);
 103
 104         memset((void *) new_text, 0, new_text_size);
 105         VARATT_SIZEP(new_text) = new_text_size;
 106         strncpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1) - VARHDRSZ);
 107         strncat(VARDATA(new_text), VARDATA(arg2), VARSIZE(arg2) - VARHDRSZ);
 108         PG_RETURN_TEXT_P(new_text);
 109 }
 110
 111 /* Composite types */
 112
 113 PG_FUNCTION_INFO_V1(c_overpaid);
 114
 115 Datum
 116 c_overpaid(PG_FUNCTION_ARGS)
 117 {
 118         TupleTableSlot *t = (TupleTableSlot *) PG_GETARG_POINTER(0);
 119         int32           limit = PG_GETARG_INT32(1);
 120         bool            isnull;
 121         int32           salary;
 122
 123         salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
 124         if (isnull)
 125                 PG_RETURN_BOOL(false);
 126
 127         /*
 128          * Alternatively, we might prefer to do PG_RETURN_NULL() for null
 129          * salary
 130          */
 131
 132         PG_RETURN_BOOL(salary > limit);
 133 }