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postgresql/contrib/tablefunc/tablefunc.c

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/*
* tablefunc
*
* Sample to demonstrate C functions which return setof scalar
* and setof composite.
* Joe Conway <mail@joeconway.com>
*
* Copyright 2002 by PostgreSQL Global Development Group
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose, without fee, and without a written agreement
* is hereby granted, provided that the above copyright notice and this
* paragraph and the following two paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHORS OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHORS AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
*/
#include <stdlib.h>
#include <math.h>
#include "postgres.h"
#include "fmgr.h"
#include "funcapi.h"
#include "executor/spi.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "tablefunc.h"
static bool compatTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2);
static void get_normal_pair(float8 *x1, float8 *x2);
static TupleDesc make_crosstab_tupledesc(TupleDesc spi_tupdesc, int num_catagories);
typedef struct
{
float8 mean; /* mean of the distribution */
float8 stddev; /* stddev of the distribution */
float8 carry_val; /* hold second generated value */
bool use_carry; /* use second generated value */
} normal_rand_fctx;
typedef struct
{
SPITupleTable *spi_tuptable; /* sql results from user query */
char *lastrowid; /* rowid of the last tuple sent */
} crosstab_fctx;
#define GET_TEXT(cstrp) DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(cstrp)))
#define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))
#define xpfree(var_) \
do { \
if (var_ != NULL) \
{ \
pfree(var_); \
var_ = NULL; \
} \
} while (0)
/*
* normal_rand - return requested number of random values
* with a Gaussian (Normal) distribution.
*
* inputs are int numvals, float8 lower_bound, and float8 upper_bound
* returns float8
*/
PG_FUNCTION_INFO_V1(normal_rand);
Datum
normal_rand(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
int call_cntr;
int max_calls;
normal_rand_fctx *fctx;
float8 mean;
float8 stddev;
float8 carry_val;
bool use_carry;
/* stuff done only on the first call of the function */
if(SRF_IS_FIRSTCALL())
{
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/* total number of tuples to be returned */
funcctx->max_calls = PG_GETARG_UINT32(0);
/* allocate memory for user context */
fctx = (normal_rand_fctx *) palloc(sizeof(normal_rand_fctx));
/*
* Use fctx to keep track of upper and lower bounds
* from call to call. It will also be used to carry over
* the spare value we get from the Box-Muller algorithm
* so that we only actually calculate a new value every
* other call.
*/
fctx->mean = PG_GETARG_FLOAT8(1);
fctx->stddev = PG_GETARG_FLOAT8(2);
fctx->carry_val = 0;
fctx->use_carry = false;
funcctx->user_fctx = fctx;
/*
* we might actually get passed a negative number, but for this
* purpose it doesn't matter, just cast it as an unsigned value
*/
srandom(PG_GETARG_UINT32(3));
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
call_cntr = funcctx->call_cntr;
max_calls = funcctx->max_calls;
fctx = funcctx->user_fctx;
mean = fctx->mean;
stddev = fctx->stddev;
carry_val = fctx->carry_val;
use_carry = fctx->use_carry;
if (call_cntr < max_calls) /* do when there is more left to send */
{
float8 result;
if(use_carry)
{
/*
* reset use_carry and use second value obtained on last pass
*/
fctx->use_carry = false;
result = carry_val;
}
else
{
float8 normval_1;
float8 normval_2;
/* Get the next two normal values */
get_normal_pair(&normval_1, &normval_2);
/* use the first */
result = mean + (stddev * normval_1);
/* and save the second */
fctx->carry_val = mean + (stddev * normval_2);
fctx->use_carry = true;
}
/* send the result */
SRF_RETURN_NEXT(funcctx, Float8GetDatum(result));
}
else /* do when there is no more left */
{
SRF_RETURN_DONE(funcctx);
}
}
/*
* get_normal_pair()
* Assigns normally distributed (Gaussian) values to a pair of provided
* parameters, with mean 0, standard deviation 1.
*
* This routine implements Algorithm P (Polar method for normal deviates)
* from Knuth's _The_Art_of_Computer_Programming_, Volume 2, 3rd ed., pages
* 122-126. Knuth cites his source as "The polar method", G. E. P. Box, M. E.
* Muller, and G. Marsaglia, _Annals_Math,_Stat._ 29 (1958), 610-611.
*
*/
static void
get_normal_pair(float8 *x1, float8 *x2)
{
float8 u1, u2, v1, v2, s;
for(;;)
{
u1 = (float8) random() / (float8) RAND_MAX;
u2 = (float8) random() / (float8) RAND_MAX;
v1 = (2.0 * u1) - 1.0;
v2 = (2.0 * u2) - 1.0;
s = pow(v1, 2) + pow(v2, 2);
if (s >= 1.0)
continue;
if (s == 0)
{
*x1 = 0;
*x2 = 0;
}
else
{
*x1 = v1 * sqrt((-2.0 * log(s)) / s);
*x2 = v2 * sqrt((-2.0 * log(s)) / s);
}
return;
}
}
/*
* crosstab - create a crosstab of rowids and values columns from a
* SQL statement returning one rowid column, one category column,
* and one value column.
*
* e.g. given sql which produces:
*
* rowid cat value
* ------+-------+-------
* row1 cat1 val1
* row1 cat2 val2
* row1 cat3 val3
* row1 cat4 val4
* row2 cat1 val5
* row2 cat2 val6
* row2 cat3 val7
* row2 cat4 val8
*
* crosstab returns:
* <===== values columns =====>
* rowid cat1 cat2 cat3 cat4
* ------+-------+-------+-------+-------
* row1 val1 val2 val3 val4
* row2 val5 val6 val7 val8
*
* NOTES:
* 1. SQL result must be ordered by 1,2.
* 2. The number of values columns depends on the tuple description
* of the function's declared return type.
* 2. Missing values (i.e. not enough adjacent rows of same rowid to
* fill the number of result values columns) are filled in with nulls.
* 3. Extra values (i.e. too many adjacent rows of same rowid to fill
* the number of result values columns) are skipped.
* 4. Rows with all nulls in the values columns are skipped.
*/
PG_FUNCTION_INFO_V1(crosstab);
Datum
crosstab(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
TupleDesc ret_tupdesc;
int call_cntr;
int max_calls;
TupleTableSlot *slot;
AttInMetadata *attinmeta;
SPITupleTable *spi_tuptable = NULL;
TupleDesc spi_tupdesc;
char *lastrowid;
crosstab_fctx *fctx;
int i;
int num_categories;
/* stuff done only on the first call of the function */
if(SRF_IS_FIRSTCALL())
{
char *sql = GET_STR(PG_GETARG_TEXT_P(0));
Oid funcid = fcinfo->flinfo->fn_oid;
Oid functypeid;
char functyptype;
TupleDesc tupdesc = NULL;
int ret;
int proc;
MemoryContext oldcontext;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/* SPI switches context on us, so save it first */
oldcontext = CurrentMemoryContext;
/* Connect to SPI manager */
if ((ret = SPI_connect()) < 0)
elog(ERROR, "crosstab: SPI_connect returned %d", ret);
/* Retrieve the desired rows */
ret = SPI_exec(sql, 0);
proc = SPI_processed;
/* Check for qualifying tuples */
if ((ret == SPI_OK_SELECT) && (proc > 0))
{
spi_tuptable = SPI_tuptable;
spi_tupdesc = spi_tuptable->tupdesc;
/*
* The provided SQL query must always return three columns.
*
* 1. rowname the label or identifier for each row in the final
* result
* 2. category the label or identifier for each column in the
* final result
* 3. values the value for each column in the final result
*/
if (spi_tupdesc->natts != 3)
elog(ERROR, "crosstab: provided SQL must return 3 columns;"
" a rowid, a category, and a values column");
}
else
{
/* no qualifying tuples */
SPI_finish();
SRF_RETURN_DONE(funcctx);
}
/* back to the original memory context */
MemoryContextSwitchTo(oldcontext);
/* get the typeid that represents our return type */
functypeid = get_func_rettype(funcid);
/* check typtype to see if we have a predetermined return type */
functyptype = get_typtype(functypeid);
if (functyptype == 'c')
{
/* Build a tuple description for a functypeid tuple */
tupdesc = TypeGetTupleDesc(functypeid, NIL);
}
else if (functyptype == 'p' && functypeid == RECORDOID)
{
if (fcinfo->nargs != 2)
elog(ERROR, "Wrong number of arguments specified for function");
else
{
int num_catagories = PG_GETARG_INT32(1);
tupdesc = make_crosstab_tupledesc(spi_tupdesc, num_catagories);
}
}
else if (functyptype == 'b')
elog(ERROR, "Invalid kind of return type specified for function");
else
elog(ERROR, "Unknown kind of return type specified for function");
/*
* Check that return tupdesc is compatible with the one we got
* from ret_relname, at least based on number and type of
* attributes
*/
if (!compatTupleDescs(tupdesc, spi_tupdesc))
elog(ERROR, "crosstab: return and sql tuple descriptions are"
" incompatible");
/* allocate a slot for a tuple with this tupdesc */
slot = TupleDescGetSlot(tupdesc);
/* assign slot to function context */
funcctx->slot = slot;
/*
* Generate attribute metadata needed later to produce tuples from raw
* C strings
*/
attinmeta = TupleDescGetAttInMetadata(tupdesc);
funcctx->attinmeta = attinmeta;
/* allocate memory for user context */
fctx = (crosstab_fctx *) palloc(sizeof(crosstab_fctx));
/*
* Save spi data for use across calls
*/
fctx->spi_tuptable = spi_tuptable;
fctx->lastrowid = NULL;
funcctx->user_fctx = fctx;
/* total number of tuples to be returned */
funcctx->max_calls = proc;
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
/*
* initialize per-call variables
*/
call_cntr = funcctx->call_cntr;
max_calls = funcctx->max_calls;
/* return slot for our tuple */
slot = funcctx->slot;
/* user context info */
fctx = (crosstab_fctx *) funcctx->user_fctx;
lastrowid = fctx->lastrowid;
spi_tuptable = fctx->spi_tuptable;
/* the sql tuple */
spi_tupdesc = spi_tuptable->tupdesc;
/* attribute return type and return tuple description */
attinmeta = funcctx->attinmeta;
ret_tupdesc = attinmeta->tupdesc;
/* the return tuple always must have 1 rowid + num_categories columns */
num_categories = ret_tupdesc->natts - 1;
if (call_cntr < max_calls) /* do when there is more left to send */
{
HeapTuple tuple;
Datum result;
char **values;
bool allnulls = true;
while (true)
{
/* allocate space */
values = (char **) palloc((1 + num_categories) * sizeof(char *));
/* and make sure it's clear */
memset(values, '\0', (1 + num_categories) * sizeof(char *));
/*
* now loop through the sql results and assign each value
* in sequence to the next category
*/
for (i = 0; i < num_categories; i++)
{
HeapTuple spi_tuple;
char *rowid;
/* see if we've gone too far already */
if (call_cntr >= max_calls)
break;
/* get the next sql result tuple */
spi_tuple = spi_tuptable->vals[call_cntr];
/* get the rowid from the current sql result tuple */
rowid = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
/*
* If this is the first pass through the values for this rowid
* set it, otherwise make sure it hasn't changed on us. Also
* check to see if the rowid is the same as that of the last
* tuple sent -- if so, skip this tuple entirely
*/
if (i == 0)
values[0] = pstrdup(rowid);
if ((rowid != NULL) && (strcmp(rowid, values[0]) == 0))
{
if ((lastrowid != NULL) && (strcmp(rowid, lastrowid) == 0))
break;
else if (allnulls == true)
allnulls = false;
/*
* Get the next category item value, which is alway attribute
* number three.
*
* Be careful to sssign the value to the array index based
* on which category we are presently processing.
*/
values[1 + i] = SPI_getvalue(spi_tuple, spi_tupdesc, 3);
/*
* increment the counter since we consume a row
* for each category, but not for last pass
* because the API will do that for us
*/
if (i < (num_categories - 1))
call_cntr = ++funcctx->call_cntr;
}
else
{
/*
* We'll fill in NULLs for the missing values,
* but we need to decrement the counter since
* this sql result row doesn't belong to the current
* output tuple.
*/
call_cntr = --funcctx->call_cntr;
break;
}
if (rowid != NULL)
xpfree(rowid);
}
xpfree(fctx->lastrowid);
if (values[0] != NULL)
lastrowid = fctx->lastrowid = pstrdup(values[0]);
if (!allnulls)
{
/* build the tuple */
tuple = BuildTupleFromCStrings(attinmeta, values);
/* make the tuple into a datum */
result = TupleGetDatum(slot, tuple);
/* Clean up */
for (i = 0; i < num_categories + 1; i++)
if (values[i] != NULL)
xpfree(values[i]);
xpfree(values);
SRF_RETURN_NEXT(funcctx, result);
}
else
{
/*
* Skipping this tuple entirely, but we need to advance
* the counter like the API would if we had returned
* one.
*/
call_cntr = ++funcctx->call_cntr;
/* we'll start over at the top */
xpfree(values);
/* see if we've gone too far already */
if (call_cntr >= max_calls)
{
/* release SPI related resources */
SPI_finish();
SRF_RETURN_DONE(funcctx);
}
}
}
}
else /* do when there is no more left */
{
/* release SPI related resources */
SPI_finish();
SRF_RETURN_DONE(funcctx);
}
}
/*
* Check if two tupdescs match in type of attributes
*/
static bool
compatTupleDescs(TupleDesc ret_tupdesc, TupleDesc sql_tupdesc)
{
int i;
Form_pg_attribute ret_attr;
Oid ret_atttypid;
Form_pg_attribute sql_attr;
Oid sql_atttypid;
/* check the rowid types match */
ret_atttypid = ret_tupdesc->attrs[0]->atttypid;
sql_atttypid = sql_tupdesc->attrs[0]->atttypid;
if (ret_atttypid != sql_atttypid)
elog(ERROR, "compatTupleDescs: SQL rowid datatype does not match"
" return rowid datatype");
/*
* - attribute [1] of the sql tuple is the category;
* no need to check it
* - attribute [2] of the sql tuple should match
* attributes [1] to [natts] of the return tuple
*/
sql_attr = sql_tupdesc->attrs[2];
for (i = 1; i < ret_tupdesc->natts; i++)
{
ret_attr = ret_tupdesc->attrs[i];
if (ret_attr->atttypid != sql_attr->atttypid)
return false;
}
/* OK, the two tupdescs are compatible for our purposes */
return true;
}
static TupleDesc
make_crosstab_tupledesc(TupleDesc spi_tupdesc, int num_catagories)
{
Form_pg_attribute sql_attr;
Oid sql_atttypid;
TupleDesc tupdesc;
int natts;
AttrNumber attnum;
char attname[NAMEDATALEN];
int i;
/*
* We need to build a tuple description with one column
* for the rowname, and num_catagories columns for the values.
* Each must be of the same type as the corresponding
* spi result input column.
*/
natts = num_catagories + 1;
tupdesc = CreateTemplateTupleDesc(natts, WITHOUTOID);
/* first the rowname column */
attnum = 1;
sql_attr = spi_tupdesc->attrs[0];
sql_atttypid = sql_attr->atttypid;
strcpy(attname, "rowname");
TupleDescInitEntry(tupdesc, attnum, attname, sql_atttypid,
-1, 0, false);
/* now the catagory values columns */
sql_attr = spi_tupdesc->attrs[2];
sql_atttypid = sql_attr->atttypid;
for (i = 0; i < num_catagories; i++)
{
attnum++;
sprintf(attname, "category_%d", i + 1);
TupleDescInitEntry(tupdesc, attnum, attname, sql_atttypid,
-1, 0, false);
}
return tupdesc;
}
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