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Refactor crosstab() to build and return a tuplestore instead of using

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value-per-call mode.  This should be more efficient in normal usage,
but the real problem with the prior coding was that it returned with
a SPI call still active.  That could cause problems if execution was
interleaved with anything else that might use SPI.
This commit is contained in:
Tom Lane 2008-12-01 01:30:18 +00:00
parent 76cc2fe6a1
commit cf407f164e
1 changed files with 208 additions and 260 deletions
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218
contrib/tablefunc/tablefunc.c
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@ -1,5 +1,5 @@
/* /*
* $PostgreSQL: pgsql/contrib/tablefunc/tablefunc.c,v 1.56 2008/11/30 23:23:52 tgl Exp $ * $PostgreSQL: pgsql/contrib/tablefunc/tablefunc.c,v 1.57 2008/12/01 01:30:18 tgl Exp $
* *
* *
* tablefunc * tablefunc
@ -94,12 +94,6 @@ typedef struct
bool use_carry; /* use second generated value */ bool use_carry; /* use second generated value */
} normal_rand_fctx; } normal_rand_fctx;
typedef struct
{
SPITupleTable *spi_tuptable; /* sql results from user query */
char *lastrowid; /* rowid of the last tuple sent */
} crosstab_fctx;
#define xpfree(var_) \ #define xpfree(var_) \
do { \ do { \
if (var_ != NULL) \ if (var_ != NULL) \
@ -356,30 +350,36 @@ PG_FUNCTION_INFO_V1(crosstab);
Datum Datum
crosstab(PG_FUNCTION_ARGS) crosstab(PG_FUNCTION_ARGS)
{ {
FuncCallContext *funcctx; char *sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
TupleDesc ret_tupdesc; ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
Tuplestorestate *tupstore;
TupleDesc tupdesc;
int call_cntr; int call_cntr;
int max_calls; int max_calls;
AttInMetadata *attinmeta; AttInMetadata *attinmeta;
SPITupleTable *spi_tuptable = NULL; SPITupleTable *spi_tuptable;
TupleDesc spi_tupdesc; TupleDesc spi_tupdesc;
char *lastrowid = NULL; bool firstpass;
crosstab_fctx *fctx; char *lastrowid;
int i; int i;
int num_categories; int num_categories;
bool firstpass = false; MemoryContext per_query_ctx;
MemoryContext oldcontext; MemoryContext oldcontext;
/* stuff done only on the first call of the function */
if (SRF_IS_FIRSTCALL())
{
char *sql = text_to_cstring(PG_GETARG_TEXT_PP(0));
TupleDesc tupdesc;
int ret; int ret;
int proc; int proc;
/* create a function context for cross-call persistence */ /* check to see if caller supports us returning a tuplestore */
funcctx = SRF_FIRSTCALL_INIT(); if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("set-valued function called in context that cannot accept a set")));
if (!(rsinfo->allowedModes & SFRM_Materialize))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("materialize mode required, but it is not " \
"allowed in this context")));
per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
/* Connect to SPI manager */ /* Connect to SPI manager */
if ((ret = SPI_connect()) < 0) if ((ret = SPI_connect()) < 0)
@ -390,9 +390,14 @@ crosstab(PG_FUNCTION_ARGS)
ret = SPI_execute(sql, true, 0); ret = SPI_execute(sql, true, 0);
proc = SPI_processed; proc = SPI_processed;
/* Check for qualifying tuples */ /* If no qualifying tuples, fall out early */
if ((ret == SPI_OK_SELECT) && (proc > 0)) if (ret != SPI_OK_SELECT || proc <= 0)
{ {
SPI_finish();
rsinfo->isDone = ExprEndResult;
PG_RETURN_NULL();
}
spi_tuptable = SPI_tuptable; spi_tuptable = SPI_tuptable;
spi_tupdesc = spi_tuptable->tupdesc; spi_tupdesc = spi_tuptable->tupdesc;
@ -413,13 +418,6 @@ crosstab(PG_FUNCTION_ARGS)
errmsg("invalid source data SQL statement"), errmsg("invalid source data SQL statement"),
errdetail("The provided SQL must return 3 " errdetail("The provided SQL must return 3 "
"columns: rowid, category, and values."))); "columns: rowid, category, and values.")));
}
else
{
/* no qualifying tuples */
SPI_finish();
SRF_RETURN_DONE(funcctx);
}
/* get a tuple descriptor for our result type */ /* get a tuple descriptor for our result type */
switch (get_call_result_type(fcinfo, NULL, &tupdesc)) switch (get_call_result_type(fcinfo, NULL, &tupdesc))
@ -451,75 +449,42 @@ crosstab(PG_FUNCTION_ARGS)
"incompatible"))); "incompatible")));
/* /*
* switch to memory context appropriate for multiple function calls * switch to long-lived memory context
*/ */
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx); oldcontext = MemoryContextSwitchTo(per_query_ctx);
/* make sure we have a persistent copy of the tupdesc */ /* make sure we have a persistent copy of the result tupdesc */
tupdesc = CreateTupleDescCopy(tupdesc); tupdesc = CreateTupleDescCopy(tupdesc);
/* initialize our tuplestore in long-lived context */
tupstore =
tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random,
false, work_mem);
MemoryContextSwitchTo(oldcontext);
/* /*
* Generate attribute metadata needed later to produce tuples from raw * Generate attribute metadata needed later to produce tuples from raw
* C strings * C strings
*/ */
attinmeta = TupleDescGetAttInMetadata(tupdesc); attinmeta = TupleDescGetAttInMetadata(tupdesc);
funcctx->attinmeta = attinmeta;
/* allocate memory for user context */ /* total number of tuples to be examined */
fctx = (crosstab_fctx *) palloc(sizeof(crosstab_fctx)); max_calls = proc;
/*
* 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);
firstpass = true;
}
/* 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;
/* 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 */ /* the return tuple always must have 1 rowid + num_categories columns */
num_categories = ret_tupdesc->natts - 1; num_categories = tupdesc->natts - 1;
if (call_cntr < max_calls) /* do when there is more left to send */ firstpass = true;
lastrowid = NULL;
for (call_cntr = 0; call_cntr < max_calls; call_cntr++)
{ {
HeapTuple tuple;
Datum result;
char **values;
bool skip_tuple = false; bool skip_tuple = false;
char **values;
while (true) /* allocate and zero space */
{ values = (char **) palloc0((1 + num_categories) * sizeof(char *));
/* 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 * now loop through the sql results and assign each value in
@ -528,7 +493,7 @@ crosstab(PG_FUNCTION_ARGS)
for (i = 0; i < num_categories; i++) for (i = 0; i < num_categories; i++)
{ {
HeapTuple spi_tuple; HeapTuple spi_tuple;
char *rowid = NULL; char *rowid;
/* see if we've gone too far already */ /* see if we've gone too far already */
if (call_cntr >= max_calls) if (call_cntr >= max_calls)
@ -554,13 +519,14 @@ crosstab(PG_FUNCTION_ARGS)
*/ */
if (!firstpass && xstreq(lastrowid, rowid)) if (!firstpass && xstreq(lastrowid, rowid))
{ {
xpfree(rowid);
skip_tuple = true; skip_tuple = true;
break; break;
} }
} }
/* /*
* If rowid hasn't changed on us, continue building the ouput * If rowid hasn't changed on us, continue building the output
* tuple. * tuple.
*/ */
if (xstreq(rowid, values[0])) if (xstreq(rowid, values[0]))
@ -576,11 +542,12 @@ crosstab(PG_FUNCTION_ARGS)
/* /*
* increment the counter since we consume a row for each * increment the counter since we consume a row for each
* category, but not for last pass because the API will do * category, but not for last pass because the outer loop
* that for us * will do that for us
*/ */
if (i < (num_categories - 1)) if (i < (num_categories - 1))
call_cntr = ++funcctx->call_cntr; call_cntr++;
xpfree(rowid);
} }
else else
{ {
@ -589,71 +556,48 @@ crosstab(PG_FUNCTION_ARGS)
* to decrement the counter since this sql result row * to decrement the counter since this sql result row
* doesn't belong to the current output tuple. * doesn't belong to the current output tuple.
*/ */
call_cntr = --funcctx->call_cntr; call_cntr--;
xpfree(rowid);
break; break;
} }
xpfree(rowid);
} }
/*
* switch to memory context appropriate for multiple function
* calls
*/
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
xpfree(fctx->lastrowid);
xpstrdup(fctx->lastrowid, values[0]);
lastrowid = fctx->lastrowid;
MemoryContextSwitchTo(oldcontext);
if (!skip_tuple) if (!skip_tuple)
{ {
HeapTuple tuple;
/* build the tuple */ /* build the tuple */
tuple = BuildTupleFromCStrings(attinmeta, values); tuple = BuildTupleFromCStrings(attinmeta, values);
/* make the tuple into a datum */ /* switch to appropriate context while storing the tuple */
result = HeapTupleGetDatum(tuple); oldcontext = MemoryContextSwitchTo(per_query_ctx);
tuplestore_puttuple(tupstore, tuple);
MemoryContextSwitchTo(oldcontext);
heap_freetuple(tuple);
}
/* Remember current rowid */
xpfree(lastrowid);
xpstrdup(lastrowid, values[0]);
firstpass = false;
/* Clean up */ /* Clean up */
for (i = 0; i < num_categories + 1; i++) for (i = 0; i < num_categories + 1; i++)
if (values[i] != NULL) if (values[i] != NULL)
xpfree(values[i]); pfree(values[i]);
xpfree(values); pfree(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 */ /* let the caller know we're sending back a tuplestore */
xpfree(values); rsinfo->returnMode = SFRM_Materialize;
rsinfo->setResult = tupstore;
rsinfo->setDesc = tupdesc;
/* see if we've gone too far already */ /* release SPI related resources (and return to caller's context) */
if (call_cntr >= max_calls)
{
/* release SPI related resources */
SPI_finish(); SPI_finish();
SRF_RETURN_DONE(funcctx);
}
/* need to reset this before the next tuple is started */ return (Datum) 0;
skip_tuple = false;
}
}
}
else
/* do when there is no more left */
{
/* release SPI related resources */
SPI_finish();
SRF_RETURN_DONE(funcctx);
}
} }
/* /*
@ -1613,6 +1557,10 @@ compatCrosstabTupleDescs(TupleDesc ret_tupdesc, TupleDesc sql_tupdesc)
Form_pg_attribute sql_attr; Form_pg_attribute sql_attr;
Oid sql_atttypid; Oid sql_atttypid;
if (ret_tupdesc->natts < 2 ||
sql_tupdesc->natts < 3)
return false;
/* check the rowid types match */ /* check the rowid types match */
ret_atttypid = ret_tupdesc->attrs[0]->atttypid; ret_atttypid = ret_tupdesc->attrs[0]->atttypid;
sql_atttypid = sql_tupdesc->attrs[0]->atttypid; sql_atttypid = sql_tupdesc->attrs[0]->atttypid;