libpq is reentrant and thread-safe if the
configure
command-line option
--enable-thread-safety
was used when the
PostgreSQL distribution was built. In
addition, you might need to use additional compiler command-line
options when you compile your application code. Refer to your
system's documentation for information about how to build
thread-enabled applications, or look in
src/Makefile.global
for PTHREAD_CFLAGS
and PTHREAD_LIBS
.
One restriction is that no two threads attempt to manipulate the same
PGconn
object at the same time. In particular, you cannot
issue concurrent commands from different threads through the same
connection object. (If you need to run concurrent commands, use
multiple connections.)
PGresult
objects are read-only after creation, and so can be
passed around freely between threads.
The deprecated functions
PQrequestCancel
,
PQoidStatus
and
fe_setauthsvc
are not thread-safe and should not be used in multithread programs.
PQrequestCancel
can be replaced by
PQcancel
.
PQoidStatus
can be replaced by
PQoidValue
.
There is no good reason to call fe_setauthsvc
at all.
libpq applications that use the
crypt
authentication method rely on the
crypt()
operating system function, which is often
not thread-safe. It is better to use the md5
method,
which is thread-safe on all platforms.
If you experience problems with threaded applications, run
the program in src/tools/thread
to see if your
platform has thread-unsafe functions. This program is run
by configure
, but for binary distributions
your library might not match the library used to build the binaries.