postgresql/contrib/tablefunc/tablefunc.c
Tom Lane c7a165adc6 Code review for HeapTupleHeader changes. Add version number to page headers
(overlaying low byte of page size) and add HEAP_HASOID bit to t_infomask,
per earlier discussion.  Simplify scheme for overlaying fields in tuple
header (no need for cmax to live in more than one place).  Don't try to
clear infomask status bits in tqual.c --- not safe to do it there.  Don't
try to force output table of a SELECT INTO to have OIDs, either.  Get rid
of unnecessarily complex three-state scheme for TupleDesc.tdhasoids, which
has already caused one recent failure.  Improve documentation.
2002-09-02 01:05:06 +00:00

646 lines
17 KiB
C

/*
* 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;
MemoryContext oldcontext;
/* 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();
/* switch to memory context appropriate for multiple function calls */
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* 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));
MemoryContextSwitchTo(oldcontext);
}
/* 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 = NULL;
crosstab_fctx *fctx;
int i;
int num_categories;
MemoryContext oldcontext;
/* 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;
/* create a function context for cross-call persistence */
funcctx = SRF_FIRSTCALL_INIT();
/* switch to memory context appropriate for multiple function calls */
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* 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);
}
/* SPI switches context on us, so reset it */
MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
/* 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;
MemoryContextSwitchTo(oldcontext);
}
/* 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 = NULL;
/* 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)
{
/* switch to memory context appropriate for multiple function calls */
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
lastrowid = fctx->lastrowid = pstrdup(values[0]);
MemoryContextSwitchTo(oldcontext);
}
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, false);
/* 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;
}