src/tutorial/funcs.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 "old style" function call conventions.
  11   See funcs_new.c for examples of "new 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 /* These prototypes just prevent possible warnings from gcc. */
  23
  24 int                     add_one(int arg);
  25 float8     *add_one_float8(float8 *arg);
  26 Point      *makepoint(Point *pointx, Point *pointy);
  27 text       *copytext(text *t);
  28 text       *concat_text(text *arg1, text *arg2);
  29 bool c_overpaid(HeapTupleHeader t,      /* the current instance of EMP */
  30                    int32 limit);
  31
  32
  33 /* By Value */
  34
  35 int
  36 add_one(int arg)
  37 {
  38         return arg + 1;
  39 }
  40
  41 /* By Reference, Fixed Length */
  42
  43 float8 *
  44 add_one_float8(float8 *arg)
  45 {
  46         float8     *result = (float8 *) palloc(sizeof(float8));
  47
  48         *result = *arg + 1.0;
  49
  50         return result;
  51 }
  52
  53 Point *
  54 makepoint(Point *pointx, Point *pointy)
  55 {
  56         Point      *new_point = (Point *) palloc(sizeof(Point));
  57
  58         new_point->x = pointx->x;
  59         new_point->y = pointy->y;
  60
  61         return new_point;
  62 }
  63
  64 /* By Reference, Variable Length */
  65
  66 text *
  67 copytext(text *t)
  68 {
  69         /*
  70          * VARSIZE is the total size of the struct in bytes.
  71          */
  72         text       *new_t = (text *) palloc(VARSIZE(t));
  73
  74         SET_VARSIZE(new_t, VARSIZE(t));
  75
  76         /*
  77          * VARDATA is a pointer to the data region of the struct.
  78          */
  79         memcpy((void *) VARDATA(new_t),         /* destination */
  80                    (void *) VARDATA(t), /* source */
  81                    VARSIZE(t) - VARHDRSZ);              /* how many bytes */
  82         return new_t;
  83 }
  84
  85 text *
  86 concat_text(text *arg1, text *arg2)
  87 {
  88         int32           arg1_size = VARSIZE(arg1) - VARHDRSZ;
  89         int32           arg2_size = VARSIZE(arg2) - VARHDRSZ;
  90         int32           new_text_size = arg1_size + arg2_size + VARHDRSZ;
  91         text       *new_text = (text *) palloc(new_text_size);
  92
  93         SET_VARSIZE(new_text, new_text_size);
  94         memcpy(VARDATA(new_text), VARDATA(arg1), arg1_size);
  95         memcpy(VARDATA(new_text) + arg1_size, VARDATA(arg2), arg2_size);
  96         return new_text;
  97 }
  98
  99 /* Composite types */
 100
 101 bool
 102 c_overpaid(HeapTupleHeader t,   /* the current instance of EMP */
 103                    int32 limit)
 104 {
 105         bool            isnull;
 106         int32           salary;
 107
 108         salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
 109         if (isnull)
 110                 return false;
 111         return salary > limit;
 112 }