Show possible triggers in EXPLAIN. #2
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okbob
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Currently the pc files use hard coded paths for "includedir" and
"libdir."
Example:
Cflags: -I/usr/include
Libs: -L/usr/lib -lpq
This is not very fortunate when cross compiling inside a buildroot,
where the includes and libs are inside a staging directory, because
this introduces host paths into the build:
checking for pkg-config... /builder/shared-workdir/build/sdk/staging_dir/host/bin/pkg-config
checking for PostgreSQL libraries via pkg_config... -L/usr/lib <----
This commit addresses this by doing the following two things:
1. Instead of hard coding the paths in "Cflags" and "Libs"
"${includedir}" and "${libdir}" are used. Note: these variables
can be overriden on the pkg-config command line
("--define-variable=libdir=/some/path").
2. Add the variables "prefix" and "exec_prefix". If "includedir"
and/or "libdir" are using these then construct them accordingly.
This is done because buildroots (for instance OpenWrt) tend to
rename the real pkg-config and call it indirectly from a script
that sets "prefix", "exec_prefix" and "bindir", like so:
pkg-config.real --define-variable=prefix=${STAGING_PREFIX} \
--define-variable=exec_prefix=${STAGING_PREFIX} \
--define-variable=bindir=${STAGING_PREFIX}/bin $@
Example #1: user calls ./configure with "--libdir=/some/lib" and
"--includedir=/some/include":
prefix=/usr/local/pgsql
exec_prefix=${prefix}
libdir=/some/lib
includedir=/some/include
Name: libpq
Description: PostgreSQL libpq library
Url: http://www.postgresql.org/
Version: 12.1
Requires:
Requires.private:
Cflags: -I${includedir}
Libs: -L${libdir} -lpq
Libs.private: -lcrypt -lm
Example #2: user calls ./configure with no arguments:
prefix=/usr/local/pgsql
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include
Name: libpq
Description: PostgreSQL libpq library
Url: http://www.postgresql.org/
Version: 12.1
Requires:
Requires.private:
Cflags: -I${includedir}
Libs: -L${libdir} -lpq
Libs.private: -lcrypt -lm
Like this the paths can be forced into the staging directory when
using a buildroot setup:
checking for pkg-config... /home/sk/tmp/openwrt/staging_dir/host/bin/pkg-config
checking for PostgreSQL libraries via pkg_config... -L/home/sk/tmp/openwrt/staging_dir/target-mips_24kc_musl/usr/lib
Author: Sebastian Kemper <sebastian_ml@gmx.net>
Co-authored-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/20200305213827.GA25135%40darth.lan
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motivation
Recently I got few times into situation where I was trying to find out what is blocking DELETE queries. Running
EXPLAIN(evenVERBOSEone) wasn't useful, since the reason was slow trigger (missing index on foreign key column). I had to create testing entry and runEXPLAIN ANALYZE DELETEto get this information.It will be really valuable for me to show triggers in
EXPLAINquery since it will make clear for me there will be any trigger "activated" during execution ofDELETEquery and that can be the reason for slowDELETE. I have added EXPLAIN option calledTRIGGERSenabled by default. There's already autoexplain property for this.I understand it is not possible to show only triggers which will be really activated unless query is really executed.
EXPLAIN ANALYZEremains untouched with this patch.I have seen initial discussion at https://www.postgresql.org/message-id/flat/20693.1111732761%40sss.pgh.pa.us to show time spent in triggers in
EXPLAIN ANALYZEincluding quick discussion to possibly show triggers duringEXPLAIN. Anyway since it doesn't show any additional cost and just inform about the possibilities, I still consider this feature useful. This is probably implementation of idea mentioned at https://www.postgresql.org/message-id/21221.1111736869%40sss.pgh.pa.us by Tom Lane:💚 All regression tests passed with this change locally.
before:
after