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As discussed on several occasions previously, the new anonymous

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composite type capability makes it possible to create a system view
based on a table function in a way that is hopefully palatable to
everyone. The attached patch takes advantage of this, moving
show_all_settings() from contrib/tablefunc into the backend (renamed
all_settings(). It is defined as a builtin returning type RECORD. During
initdb a system view is created to expose the same information presently
available through SHOW ALL. For example:

test=# select * from pg_settings where name like '%debug%';
          name          | setting
-----------------------+---------
  debug_assertions      | on
  debug_pretty_print    | off
  debug_print_parse     | off
  debug_print_plan      | off
  debug_print_query     | off
  debug_print_rewritten | off
  wal_debug             | 0
(7 rows)


Additionally during initdb two rules are created which make it possible
to change settings by updating the system view -- a "virtual table" as
Tom put it. Here's an example:

Joe Conway
This commit is contained in:
Bruce Momjian
2002-08-15 02:51:27 +00:00
parent 4c4854c458
commit 45e2544584
10 changed files with 372 additions and 220 deletions
Download Patch File Download Diff File Expand all files Collapse all files

114
src/backend/utils/misc/guc.c
View File

@ -5,7 +5,7 @@
* command, configuration file, and command line options.
* See src/backend/utils/misc/README for more information.
*
* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.81 2002/08/14 23:02:59 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.82 2002/08/15 02:51:26 momjian Exp $
*
* Copyright 2000 by PostgreSQL Global Development Group
* Written by Peter Eisentraut <peter_e@gmx.net>.
@ -29,6 +29,7 @@
#include "commands/vacuum.h"
#include "executor/executor.h"
#include "fmgr.h"
#include "funcapi.h"
#include "libpq/auth.h"
#include "libpq/pqcomm.h"
#include "mb/pg_wchar.h"
@ -2403,6 +2404,117 @@ show_config_by_name(PG_FUNCTION_ARGS)
PG_RETURN_TEXT_P(result_text);
}
/*
* show_all_settings - equiv to SHOW ALL command but implemented as
* a Table Function.
*/
Datum
show_all_settings(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
TupleDesc tupdesc;
int call_cntr;
int max_calls;
TupleTableSlot *slot;
AttInMetadata *attinmeta;
/* 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();
/* need a tuple descriptor representing two TEXT columns */
tupdesc = CreateTemplateTupleDesc(2, WITHOUTOID);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "name",
TEXTOID, -1, 0, false);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "setting",
TEXTOID, -1, 0, false);
/* 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;
/* total number of tuples to be returned */
funcctx->max_calls = GetNumConfigOptions();
}
/* stuff done on every call of the function */
funcctx = SRF_PERCALL_SETUP();
call_cntr = funcctx->call_cntr;
max_calls = funcctx->max_calls;
slot = funcctx->slot;
attinmeta = funcctx->attinmeta;
if (call_cntr < max_calls) /* do when there is more left to send */
{
char **values;
char *varname;
char *varval;
bool noshow;
HeapTuple tuple;
Datum result;
/*
* Get the next visible GUC variable name and value
*/
do
{
varval = GetConfigOptionByNum(call_cntr, (const char **) &varname, &noshow);
if (noshow)
{
/* varval is a palloc'd copy, so free it */
if (varval != NULL)
pfree(varval);
/* bump the counter and get the next config setting */
call_cntr = ++funcctx->call_cntr;
/* make sure we haven't gone too far now */
if (call_cntr >= max_calls)
SRF_RETURN_DONE(funcctx);
}
} while (noshow);
/*
* Prepare a values array for storage in our slot.
* This should be an array of C strings which will
* be processed later by the appropriate "in" functions.
*/
values = (char **) palloc(2 * sizeof(char *));
values[0] = pstrdup(varname);
values[1] = varval; /* varval is already a palloc'd copy */
/* build a tuple */
tuple = BuildTupleFromCStrings(attinmeta, values);
/* make the tuple into a datum */
result = TupleGetDatum(slot, tuple);
/* Clean up */
pfree(values[0]);
if (varval != NULL)
pfree(values[1]);
pfree(values);
SRF_RETURN_NEXT(funcctx, result);
}
else /* do when there is no more left */
{
SRF_RETURN_DONE(funcctx);
}
}
static char *
_ShowOption(struct config_generic *record)
{