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jconwayjconway
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Add new system view, pg_config
Move and refactor the underlying code for the pg_config client application to src/common in support of sharing it with a new system information SRF called pg_config() which makes the same information available via SQL. Additionally wrap the SRF with a new system view, as called pg_config. Patch by me with extensive input and review by Michael Paquier and additional review by Alvaro Herrera.
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‎doc/src/sgml/catalogs.sgml‎

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<entry>available versions of extensions</entry>
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</row>
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<row>
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<entry><link linkend="view-pg-config"><structname>pg_config</structname></link></entry>
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<entry>compile-time configuration parameters</entry>
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</row>
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<row>
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<entry><link linkend="view-pg-cursors"><structname>pg_cursors</structname></link></entry>
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<entry>open cursors</entry>
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</para>
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</sect1>
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<sect1 id="view-pg-config">
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<title><structname>pg_config</structname></title>
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<indexterm zone="view-pg-config">
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<primary>pg_config</primary>
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</indexterm>
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<para>
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The view <structname>pg_config</structname> describes the
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compile-time configuration parameters of the currently installed
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version of <productname>PostgreSQL</>. It is intended, for example, to
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be used by software packages that want to interface to
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<productname>PostgreSQL</> to facilitate finding the required header
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files and libraries. It provides the same basic information as the
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<xref linkend="app-pgconfig"> <productname>PostgreSQL</> Client
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Application.
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</para>
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<table>
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<title><structname>pg_config</> Columns</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Type</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><structfield>name</structfield></entry>
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<entry><type>text</type></entry>
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<entry>The parameter name</entry>
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</row>
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<row>
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<entry><structfield>setting</structfield></entry>
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<entry><type>text</type></entry>
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<entry>The parameter value</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</sect1>
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<sect1 id="view-pg-cursors">
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<title><structname>pg_cursors</structname></title>
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‎src/backend/catalog/system_views.sql‎

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@@ -433,6 +433,12 @@ CREATE VIEW pg_timezone_abbrevs AS
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CREATE VIEW pg_timezone_names AS
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SELECT * FROM pg_timezone_names();
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CREATE VIEW pg_config AS
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SELECT * FROM pg_config();
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REVOKE ALL on pg_config FROM PUBLIC;
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REVOKE EXECUTE ON FUNCTION pg_config() FROM PUBLIC;
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-- Statistics views
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CREATE VIEW pg_stat_all_tables AS

‎src/backend/utils/misc/Makefile‎

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@@ -14,8 +14,8 @@ include $(top_builddir)/src/Makefile.global
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override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
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OBJS = guc.o help_config.o pg_rusage.o ps_status.o rls.o \
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sampling.o superuser.o timeout.o tzparser.o
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OBJS = guc.o help_config.o pg_config.o pg_rusage.o \
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ps_status.o rls.o sampling.o superuser.o timeout.o tzparser.o
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# This location might depend on the installation directories. Therefore
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# we can't subsitute it into pg_config.h.

‎src/backend/utils/misc/pg_config.c‎

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/*-------------------------------------------------------------------------
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*
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* pg_config.c
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* Expose same output as pg_config except as an SRF
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*
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/backend/utils/misc/pg_config.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "funcapi.h"
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#include "miscadmin.h"
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#include "catalog/pg_type.h"
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#include "common/config_info.h"
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#include "utils/builtins.h"
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#include "utils/elog.h"
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#include "port.h"
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Datum
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pg_config(PG_FUNCTION_ARGS)
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{
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ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
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Tuplestorestate *tupstore;
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HeapTuple tuple;
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TupleDesc tupdesc;
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AttInMetadata *attinmeta;
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MemoryContext per_query_ctx;
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MemoryContext oldcontext;
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ConfigData *configdata;
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size_t configdata_len;
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char *values[2];
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int i = 0;
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/* check to see if caller supports us returning a tuplestore */
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if (!rsinfo || !(rsinfo->allowedModes & SFRM_Materialize))
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("materialize mode required, but it is not "
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"allowed in this context")));
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per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
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oldcontext = MemoryContextSwitchTo(per_query_ctx);
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/* get the requested return tuple description */
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tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
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/*
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* Check to make sure we have a reasonable tuple descriptor
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*/
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if (tupdesc->natts != 2 ||
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tupdesc->attrs[0]->atttypid != TEXTOID ||
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tupdesc->attrs[1]->atttypid != TEXTOID)
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ereport(ERROR,
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(errcode(ERRCODE_SYNTAX_ERROR),
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errmsg("query-specified return tuple and "
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"function return type are not compatible")));
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/* OK to use it */
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attinmeta = TupleDescGetAttInMetadata(tupdesc);
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/* let the caller know we're sending back a tuplestore */
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rsinfo->returnMode = SFRM_Materialize;
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/* initialize our tuplestore */
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tupstore = tuplestore_begin_heap(true, false, work_mem);
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configdata = get_configdata(my_exec_path, &configdata_len);
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for (i = 0; i < configdata_len; i++)
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{
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values[0] = configdata[i].name;
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values[1] = configdata[i].setting;
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tuple = BuildTupleFromCStrings(attinmeta, values);
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tuplestore_puttuple(tupstore, tuple);
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}
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/*
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* no longer need the tuple descriptor reference created by
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* TupleDescGetAttInMetadata()
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*/
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ReleaseTupleDesc(tupdesc);
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tuplestore_donestoring(tupstore);
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rsinfo->setResult = tupstore;
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/*
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* SFRM_Materialize mode expects us to return a NULL Datum. The actual
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* tuples are in our tuplestore and passed back through
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* rsinfo->setResult. rsinfo->setDesc is set to the tuple description
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* that we actually used to build our tuples with, so the caller can
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* verify we did what it was expecting.
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*/
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rsinfo->setDesc = tupdesc;
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MemoryContextSwitchTo(oldcontext);
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return (Datum) 0;
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}

‎src/bin/pg_config/Makefile‎

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OBJS= pg_config.o $(WIN32RES)
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# don't include subdirectory-path-dependent -I and -L switches
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STD_CPPFLAGS := $(filter-out -I$(top_srcdir)/src/include -I$(top_builddir)/src/include,$(CPPFLAGS))
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STD_LDFLAGS := $(filter-out -L$(top_builddir)/src/port,$(LDFLAGS))
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override CPPFLAGS += -DVAL_CONFIGURE="\"$(configure_args)\""
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override CPPFLAGS += -DVAL_CC="\"$(CC)\""
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override CPPFLAGS += -DVAL_CPPFLAGS="\"$(STD_CPPFLAGS)\""
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override CPPFLAGS += -DVAL_CFLAGS="\"$(CFLAGS)\""
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override CPPFLAGS += -DVAL_CFLAGS_SL="\"$(CFLAGS_SL)\""
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override CPPFLAGS += -DVAL_LDFLAGS="\"$(STD_LDFLAGS)\""
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override CPPFLAGS += -DVAL_LDFLAGS_EX="\"$(LDFLAGS_EX)\""
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override CPPFLAGS += -DVAL_LDFLAGS_SL="\"$(LDFLAGS_SL)\""
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override CPPFLAGS += -DVAL_LIBS="\"$(LIBS)\""
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all: pg_config
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pg_config: $(OBJS) | submake-libpgport

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