Add PQisthreadsafe() to libpq, to allow library applications to query

the thread-safety status of the library.

doc/src/sgml/libpq.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.210 2006/05/21 20:19:23 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.211 2006/05/23 22:13:19 momjian Exp $ -->
 
  <chapter id="libpq">
   <title><application>libpq</application> - C Library</title>
@@ -4196,11 +4196,32 @@ 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 
 <filename>src/Makefile.global</filename> for <literal>PTHREAD_CFLAGS</>
-and <literal>PTHREAD_LIBS</>.
+and <literal>PTHREAD_LIBS</>.  This function allows the querying of
+<application>libpq</application>'s thread-safe status:
+</para>
+
+<variablelist>
+<varlistentry>
+<term><function>PQisthreadsafe</function><indexterm><primary>PQisthreadsafe</></></term>
+<listitem>
+<para>
+       Returns the thread safety status of the <application>libpq</application>
+       library.
+<synopsis>
+int PQisthreadsafe();
+</synopsis>
 </para>
 
 <para>
-One restriction is that no two threads attempt to manipulate the same
+       Returns 1 if the <application>libpq</application> is thead-safe and
+       0 if it is not.
+</para>
+</listitem>
+</varlistentry>
+</variablelist>
+
+<para>
+One thread restriction is that no two threads attempt to manipulate the same
 <structname>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

src/interfaces/libpq/exports.txt

@@ -1,4 +1,4 @@
-# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.8 2006/05/21 20:19:23 tgl Exp $
+# $PostgreSQL: pgsql/src/interfaces/libpq/exports.txt,v 1.9 2006/05/23 22:13:19 momjian Exp $
 # Functions to be exported by libpq DLLs
 PQconnectdb               1
 PQsetdbLogin              2
@@ -128,3 +128,5 @@ PQregisterThreadLock      125
 PQescapeStringConn        126
 PQescapeByteaConn         127
 PQencryptPassword         128
+PQisthreadsafe            129
+

src/interfaces/libpq/fe-exec.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.183 2006/05/21 20:19:23 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-exec.c,v 1.184 2006/05/23 22:13:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2343,6 +2343,18 @@ PQisnonblocking(const PGconn *conn)
 	return pqIsnonblocking(conn);
 }
 
+/* libpq is thread-safe? */
+int
+PQisthreadsafe(void)
+{
+#ifdef ENABLE_THREAD_SAFETY
+	return true;
+#else
+	return false;
+#endif
+}
+
+
 /* try to force data out, really only useful for non-blocking users */
 int
 PQflush(PGconn *conn)

src/interfaces/libpq/libpq-fe.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.128 2006/05/21 20:19:23 tgl Exp $
+ * $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.129 2006/05/23 22:13:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -366,6 +366,7 @@ extern int	PQendcopy(PGconn *conn);
 /* Set blocking/nonblocking connection to the backend */
 extern int	PQsetnonblocking(PGconn *conn, int arg);
 extern int	PQisnonblocking(const PGconn *conn);
+extern int	PQisthreadsafe(void);
 
 /* Force the write buffer to be written (or at least try) */
 extern int	PQflush(PGconn *conn);