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/******************************************************************************
These are user-defined functions that can be bound to a Postgres backend
and called by Postgres to execute SQL functions of the same name.
The calling format for these functions is defined by the CREATE FUNCTION
SQL statement that binds them to the backend.
NOTE: this file shows examples of "new style" function call conventions.
See funcs.c for examples of "old style".
*****************************************************************************/
#include <string.h>
#include "postgres.h" /* general Postgres declarations */
#include "fmgr.h" /* for argument/result macros */
#include "executor/executor.h" /* for GetAttributeByName() */
#include "utils/geo_decls.h" /* for point type */
/* These prototypes just prevent possible warnings from gcc. */
Datum add_one(PG_FUNCTION_ARGS);
Datum add_one_float8(PG_FUNCTION_ARGS);
Datum makepoint(PG_FUNCTION_ARGS);
Datum copytext(PG_FUNCTION_ARGS);
Datum concat_text(PG_FUNCTION_ARGS);
Datum c_overpaid(PG_FUNCTION_ARGS);
/* By Value */
PG_FUNCTION_INFO_V1(add_one);
Datum
add_one(PG_FUNCTION_ARGS)
{
int32 arg = PG_GETARG_INT32(0);
PG_RETURN_INT32(arg + 1);
}
/* By Reference, Fixed Length */
PG_FUNCTION_INFO_V1(add_one_float8);
Datum
add_one_float8(PG_FUNCTION_ARGS)
{
/* The macros for FLOAT8 hide its pass-by-reference nature */
float8 arg = PG_GETARG_FLOAT8(0);
PG_RETURN_FLOAT8(arg + 1.0);
}
PG_FUNCTION_INFO_V1(makepoint);
Datum
makepoint(PG_FUNCTION_ARGS)
{
Point *pointx = PG_GETARG_POINT_P(0);
Point *pointy = PG_GETARG_POINT_P(1);
Point *new_point = (Point *) palloc(sizeof(Point));
new_point->x = pointx->x;
new_point->y = pointy->y;
PG_RETURN_POINT_P(new_point);
}
/* By Reference, Variable Length */
PG_FUNCTION_INFO_V1(copytext);
Datum
copytext(PG_FUNCTION_ARGS)
{
text *t = PG_GETARG_TEXT_P(0);
/*
* VARSIZE is the total size of the struct in bytes.
*/
text *new_t = (text *) palloc(VARSIZE(t));
VARATT_SIZEP(new_t) = VARSIZE(t);
/*
* VARDATA is a pointer to the data region of the struct.
*/
memcpy((void *) VARDATA(new_t), /* destination */
(void *) VARDATA(t), /* source */
VARSIZE(t)-VARHDRSZ); /* how many bytes */
PG_RETURN_TEXT_P(new_t);
}
PG_FUNCTION_INFO_V1(concat_text);
Datum
concat_text(PG_FUNCTION_ARGS)
{
text *arg1 = PG_GETARG_TEXT_P(0);
text *arg2 = PG_GETARG_TEXT_P(1);
int32 new_text_size = VARSIZE(arg1) + VARSIZE(arg2) - VARHDRSZ;
text *new_text = (text *) palloc(new_text_size);
memset((void *) new_text, 0, new_text_size);
VARATT_SIZEP(new_text) = new_text_size;
strncpy(VARDATA(new_text), VARDATA(arg1), VARSIZE(arg1)-VARHDRSZ);
strncat(VARDATA(new_text), VARDATA(arg2), VARSIZE(arg2)-VARHDRSZ);
PG_RETURN_TEXT_P(new_text);
}
/* Composite types */
PG_FUNCTION_INFO_V1(c_overpaid);
Datum
c_overpaid(PG_FUNCTION_ARGS)
{
TupleTableSlot *t = (TupleTableSlot *) PG_GETARG_POINTER(0);
int32 limit = PG_GETARG_INT32(1);
bool isnull;
int32 salary;
salary = DatumGetInt32(GetAttributeByName(t, "salary", &isnull));
if (isnull)
PG_RETURN_BOOL(false);
/* Alternatively, we might prefer to do PG_RETURN_NULL() for null salary */
PG_RETURN_BOOL(salary > limit);
}
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