libpq is reentrant and thread-safe by default.
You might need to use special 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. This function allows the querying of
libpq's thread-safe status:
PQisthreadsafe #Returns the thread safety status of the libpq library.
int PQisthreadsafe();
Returns 1 if the libpq is thread-safe and 0 if it is not.
One thread 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 normally read-only after creation,
and so can be passed around freely between threads. However, if you use
any of the PGresult-modifying functions described in
Section 36.12 or Section 36.14, it's up
to you to avoid concurrent operations on the same PGresult,
too.
The deprecated functions PQrequestCancel and
PQoidStatus are not thread-safe and should not be
used in multithread programs. PQrequestCancel
can be replaced by PQcancel.
PQoidStatus can be replaced by
PQoidValue.
If you are using Kerberos inside your application (in addition to inside
libpq), you will need to do locking around
Kerberos calls because Kerberos functions are not thread-safe. See
function PQregisterThreadLock in the
libpq source code for a way to do cooperative
locking between libpq and your application.