src/tutorial/funcs.c

   1 /* src/tutorial/funcs.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
  11 #include "postgres.h"                   /* general Postgres declarations */
  12
  13 #include "executor/executor.h"  /* for GetAttributeByName() */
  14 #include "utils/geo_decls.h"    /* for point type */
  15
  16 PG_MODULE_MAGIC;
  17
  18
  19 /* By Value */
  20
  21 PG_FUNCTION_INFO_V1(add_one);
  22
  23 Datum
  24 add_one(PG_FUNCTION_ARGS)
  25 {
  26         int32           arg = PG_GETARG_INT32(0);
  27
  28         PG_RETURN_INT32(arg + 1);
  29 }
  30
  31 /* By Reference, Fixed Length */
  32
  33 PG_FUNCTION_INFO_V1(add_one_float8);
  34
  35 Datum
  36 add_one_float8(PG_FUNCTION_ARGS)
  37 {
  38         /* The macros for FLOAT8 hide its pass-by-reference nature */
  39         float8          arg = PG_GETARG_FLOAT8(0);
  40
  41         PG_RETURN_FLOAT8(arg + 1.0);
  42 }
  43
  44 PG_FUNCTION_INFO_V1(makepoint);
  45
  46 Datum
  47 makepoint(PG_FUNCTION_ARGS)
  48 {
  49         Point      *pointx = PG_GETARG_POINT_P(0);
  50         Point      *pointy = PG_GETARG_POINT_P(1);
  51         Point      *new_point = (Point *) palloc(sizeof(Point));
  52
  53         new_point->x = pointx->x;
  54         new_point->y = pointy->y;
  55
  56         PG_RETURN_POINT_P(new_point);
  57 }
  58
  59 /* By Reference, Variable Length */
  60
  61 PG_FUNCTION_INFO_V1(copytext);
  62
  63 Datum
  64 copytext(PG_FUNCTION_ARGS)
  65 {
  66         text       *t = PG_GETARG_TEXT_PP(0);
  67
  68         /*
  69          * VARSIZE_ANY_EXHDR is the size of the struct in bytes, minus the
  70          * VARHDRSZ or VARHDRSZ_SHORT of its header.  Construct the copy with a
  71          * full-length header.
  72          */
  73         text       *new_t = (text *) palloc(VARSIZE_ANY_EXHDR(t) + VARHDRSZ);
  74
  75         SET_VARSIZE(new_t, VARSIZE_ANY_EXHDR(t) + VARHDRSZ);
  76
  77         /*
  78          * VARDATA is a pointer to the data region of the new struct.  The source
  79          * could be a short datum, so retrieve its data through VARDATA_ANY.
  80          */
  81         memcpy((void *) VARDATA(new_t), /* destination */
  82                    (void *) VARDATA_ANY(t), /* source */
  83                    VARSIZE_ANY_EXHDR(t));       /* 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_PP(0);
  93         text       *arg2 = PG_GETARG_TEXT_PP(1);
  94         int32           arg1_size = VARSIZE_ANY_EXHDR(arg1);
  95         int32           arg2_size = VARSIZE_ANY_EXHDR(arg2);
  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_ANY(arg1), arg1_size);
 101         memcpy(VARDATA(new_text) + arg1_size, VARDATA_ANY(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 }