|PostgreSQL Reference Manual - Volume 2 - Programming Guide|
by The PostgreSQL Global Development Group
Paperback (6"x9"), 408 pages
RRP £19.95 ($34.95)
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1.17 Behavior in Threaded Programs
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
PTHREAD_LIBS. This function allows the querying of
libpq's thread-safe status:
Returns the thread safety status of the libpq
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
PGresult objects are read-only after creation, and so can be
passed around freely between threads.
The deprecated functions
are not thread-safe and should not be used in multithread programs.
PQrequestCancel can be replaced by
PQoidStatus can be replaced by
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
PQregisterThreadLock in the
libpq source code for a way to do cooperative
locking between libpq and your application.
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.
|ISBN 0954612035||PostgreSQL Reference Manual - Volume 2 - Programming Guide||See the print edition|