PostgreSQL 9.6 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.

pg_config is not a tool used in everyday work, as it provides information that is related to compilation of PostgreSQL, like:

=$ pg_config BINDIR = /home/pgdba/work/bin DOCDIR = /home/pgdba/work/share/doc/postgresql HTMLDIR = /home/pgdba/work/share/doc/postgresql INCLUDEDIR = /home/pgdba/work/include PKGINCLUDEDIR = /home/pgdba/work/include/postgresql INCLUDEDIR-SERVER = /home/pgdba/work/include/postgresql/server LIBDIR = /home/pgdba/work/lib PKGLIBDIR = /home/pgdba/work/lib/postgresql LOCALEDIR = /home/pgdba/work/share/locale MANDIR = /home/pgdba/work/share/man SHAREDIR = /home/pgdba/work/share/postgresql SYSCONFDIR = /home/pgdba/work/etc/postgresql PGXS = /home/pgdba/work/lib/postgresql/pgxs/src/makefiles/pgxs.mk CONFIGURE = '--prefix=/home/pgdba/work' '--enable-debug' '--with-pgport=5960' '--with-tcl' '--with-perl' '--with-python' '--enable-integer-datetimes' '--without-pam' '--without-bonjour' '--without-openssl' '--with-uuid=ossp' '--with-readline' '--with-libxml' '--with-zlib' '--with-gnu-ld' CC = gcc CPPFLAGS = -DFRONTEND -D_GNU_SOURCE -I/usr/include/libxml2 CFLAGS = -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O2 CFLAGS_SL = -fpic LDFLAGS = -L../../src/common -Wl,--as-needed -Wl,-rpath,'/home/pgdba/work/lib',--enable-new-dtags LDFLAGS_EX = LDFLAGS_SL = LIBS = -lpgcommon -lpgport -lxml2 -lz -lreadline -lrt -lcrypt -ldl -lm VERSION = PostgreSQL 9.6devel

But it is nice in a way that it shows paths, and specific options that this PostgreSQL was compiled with.

And now, thanks to Joe, Michael, and Alvaro – we get this information also in form of sql view:

$ select * from pg_config order by 1; name | setting -------------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- BINDIR | /home/pgdba/work/bin CC | gcc CFLAGS | -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -g -O2 CFLAGS_SL | -fpic CONFIGURE | '--prefix=/home/pgdba/work' '--enable-debug' '--with-pgport=5960' '--with-tcl' '--with-perl' '--with-python' '--enable-integer-datetimes' '--without-pam' '--without-bonjour' '--without-openssl' '--with-uuid=ossp' '--with-readline' '--with-libxml' '--with-zlib' '--with-gnu-ld' CPPFLAGS | -D_GNU_SOURCE -I/usr/include/libxml2 DOCDIR | /home/pgdba/work/share/doc/postgresql HTMLDIR | /home/pgdba/work/share/doc/postgresql INCLUDEDIR | /home/pgdba/work/include INCLUDEDIR-SERVER | /home/pgdba/work/include/postgresql/server LDFLAGS | -L../../src/common -Wl,--as-needed -Wl,-rpath,'/home/pgdba/work/lib',--enable-new-dtags LDFLAGS_EX | LDFLAGS_SL | LIBDIR | /home/pgdba/work/lib LIBS | -lpgcommon -lpgport -lxml2 -lz -lreadline -lrt -lcrypt -ldl -lm LOCALEDIR | /home/pgdba/work/share/locale MANDIR | /home/pgdba/work/share/man PGXS | /home/pgdba/work/lib/postgresql/pgxs/src/makefiles/pgxs.mk PKGINCLUDEDIR | /home/pgdba/work/include/postgresql PKGLIBDIR | /home/pgdba/work/lib/postgresql SHAREDIR | /home/pgdba/work/share/postgresql SYSCONFDIR | /home/pgdba/work/etc/postgresql VERSION | PostgreSQL 9.6devel (23 rows)

I don't think it will be useful in day-to-day work, but I did stumble, couple of times, on cases where such information would be very helpful. So – thanks a lot guys, I appreciate it.