37.18. Extension Building Infrastructure
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If you are thinking about distributing your PostgreSQL extension modules, setting up a portable build system for them can be fairly difficult. Therefore the PostgreSQL installation provides a build infrastructure for extensions, called PGXS, so that simple extension modules can be built simply against an already installed server. PGXS is mainly intended for extensions that include C code, although it can be used for pure-SQL extensions too. Note that PGXS is not intended to be a universal build system framework that can be used to build any software interfacing to PostgreSQL; it simply automates common build rules for simple server extension modules. For more complicated packages, you might need to write your own build system.
To use the PGXS infrastructure for your extension, you must write a simple makefile. In the makefile, you need to set some variables and include the global PGXS makefile. Here is an example that builds an extension module named isbn_issn, consisting of a shared library containing some C code, an extension control file, a SQL script, an include file (only needed if other modules might need to access the extension functions without going via SQL), and a documentation text file:
The last three lines should always be the same. Earlier in the file, you assign variables or add custom make rules.
Set one of these three variables to specify what is built:MODULES
list of shared-library objects to be built from source files with same stem (do not include library suffixes in this list)MODULE_big
a shared library to build from multiple source files (list object files in OBJS)PROGRAM
an executable program to build (list object files in OBJS)
The following variables can also be set:EXTENSION
extension name(s); for each name you must provide an extension.control file, which will be installed into prefix/share/extensionMODULEDIR
subdirectory of prefix/share into which DATA and DOCS files should be installed (if not set, default is extension if EXTENSION is set, or contrib if not)DATA
random files to install into prefix/share/$MODULEDIRDATA_built
random files to install into prefix/share/$MODULEDIR, which need to be built firstDATA_TSEARCH
random files to install under prefix/share/tsearch_dataDOCS
random files to install under prefix/doc/$MODULEDIRHEADERS
HEADERS_built
Files to (optionally build and) install under prefix/include/server/$MODULEDIR/$MODULE_big.
Unlike DATA_built, files in HEADERS_built are not removed by the clean target; if you want them removed, also add them to EXTRA_CLEAN or add your own rules to do it.HEADERS_$MODULE
HEADERS_built_$MODULE
Files to install (after building if specified) under prefix/include/server/$MODULEDIR/$MODULE, where $MODULE must be a module name used in MODULES or MODULE_big.
Unlike DATA_built, files in HEADERS_built_$MODULE are not removed by the clean target; if you want them removed, also add them to EXTRA_CLEAN or add your own rules to do it.
It is legal to use both variables for the same module, or any combination, unless you have two module names in the MODULES list that differ only by the presence of a prefix built_, which would cause ambiguity. In that (hopefully unlikely) case, you should use only the HEADERS_built_$MODULE variables.SCRIPTS
script files (not binaries) to install into prefix/binSCRIPTS_built
script files (not binaries) to install into prefix/bin, which need to be built firstREGRESS
list of regression test cases (without suffix), see belowREGRESS_OPTS
additional switches to pass to pg_regressISOLATION
list of isolation test cases, see below for more detailsISOLATION_OPTS
additional switches to pass to pg_isolation_regressTAP_TESTS
switch defining if TAP tests need to be run, see belowNO_INSTALLCHECK
don't define an installcheck target, useful e.g. if tests require special configuration, or don't use pg_regressEXTRA_CLEAN
extra files to remove in make cleanPG_CPPFLAGS
will be prepended to CPPFLAGSPG_CFLAGS
will be appended to CFLAGSPG_CXXFLAGS
will be appended to CXXFLAGSPG_LDFLAGS
will be prepended to LDFLAGSPG_LIBS
will be added to PROGRAM link lineSHLIB_LINK
will be added to MODULE_big link linePG_CONFIG
path to pg_config program for the PostgreSQL installation to build against (typically just pg_config to use the first one in your PATH)
Put this makefile as Makefile in the directory which holds your extension. Then you can do make to compile, and then make install to install your module. By default, the extension is compiled and installed for the PostgreSQL installation that corresponds to the first pg_config program found in your PATH. You can use a different installation by setting PG_CONFIG to point to its pg_config program, either within the makefile or on the make command line.
You can also run make in a directory outside the source tree of your extension, if you want to keep the build directory separate. This procedure is also called a VPATH build. Here's how:
Alternatively, you can set up a directory for a VPATH build in a similar way to how it is done for the core code. One way to do this is using the core script config/prep_buildtree. Once this has been done you can build by setting the make variable VPATH like this:
This procedure can work with a greater variety of directory layouts.
The scripts listed in the REGRESS variable are used for regression testing of your module, which can be invoked by make installcheck after doing make install. For this to work you must have a running PostgreSQL server. The script files listed in REGRESS must appear in a subdirectory named sql/ in your extension's directory. These files must have extension .sql, which must not be included in the REGRESS list in the makefile. For each test there should also be a file containing the expected output in a subdirectory named expected/, with the same stem and extension .out. make installcheck executes each test script with psql, and compares the resulting output to the matching expected file. Any differences will be written to the file regression.diffs in diff -c format. Note that trying to run a test that is missing its expected file will be reported as “trouble”, so make sure you have all expected files.
The scripts listed in the ISOLATION variable are used for tests stressing behavior of concurrent session with your module, which can be invoked by make installcheck after doing make install. For this to work you must have a running PostgreSQL server. The script files listed in ISOLATION must appear in a subdirectory named specs/ in your extension's directory. These files must have extension .spec, which must not be included in the ISOLATION list in the makefile. For each test there should also be a file containing the expected output in a subdirectory named expected/, with the same stem and extension .out. make installcheck executes each test script, and compares the resulting output to the matching expected file. Any differences will be written to the file output_iso/regression.diffs in diff -c format. Note that trying to run a test that is missing its expected file will be reported as “trouble”, so make sure you have all expected files.
TAP_TESTS enables the use of TAP tests. Data from each run is present in a subdirectory named tmp_check/. See also Section 32.4 for more details.
Tip
The easiest way to create the expected files is to create empty files, then do a test run (which will of course report differences). Inspect the actual result files found in the results/ directory (for tests in REGRESS), or output_iso/results/ directory (for tests in ISOLATION), then copy them to expected/ if they match what you expect from the test.
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