Add a feature for automatic initialization and finalization of dynamically

loaded libraries: call functions _PG_init() and _PG_fini() if the library
defines such symbols.  Hence we no longer need to specify an initialization
function in preload_libraries: we can assume that the library used the
_PG_init() convention, instead.  This removes one source of pilot error
in use of preloaded libraries.  Original patch by Ralf Engelschall,
preload_libraries changes by me.

5 files changed, 54 insertions, 123 deletions

diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index 2ed16b12cbe..8e0f309d056 100644
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1,7 +1,7 @@
 /**********************************************************************
  * plperl.c - perl as a procedural language for PostgreSQL
  *
- *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.112 2006/06/16 18:42:23 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.113 2006/08/08 19:15:09 tgl Exp $
  *
  **********************************************************************/
 
@@ -87,7 +87,6 @@ typedef struct plperl_query_desc
 /**********************************************************************
  * Global data
  **********************************************************************/
-static bool plperl_firstcall = true;
 static bool plperl_safe_init_done = false;
 static PerlInterpreter *plperl_interp = NULL;
 static HV  *plperl_proc_hash = NULL;
@@ -101,12 +100,11 @@ static plperl_call_data *current_call_data = NULL;
 /**********************************************************************
  * Forward declarations
  **********************************************************************/
-static void plperl_init_all(void);
-static void plperl_init_interp(void);
-
 Datum		plperl_call_handler(PG_FUNCTION_ARGS);
 Datum		plperl_validator(PG_FUNCTION_ARGS);
-void		plperl_init(void);
+void		_PG_init(void);
+
+static void plperl_init_interp(void);
 
 static Datum plperl_func_handler(PG_FUNCTION_ARGS);
 
@@ -135,16 +133,21 @@ perm_fmgr_info(Oid functionId, FmgrInfo *finfo)
 }
 
 
-/* Perform initialization during postmaster startup. */
-
+/*
+ * _PG_init()			- library load-time initialization
+ *
+ * DO NOT make this static nor change its name!
+ */
 void
-plperl_init(void)
+_PG_init(void)
 {
-	if (!plperl_firstcall)
+	/* Be sure we do initialization only once (should be redundant now) */
+	static bool inited = false;
+
+	if (inited)
 		return;
 
-	DefineCustomBoolVariable(
-							 "plperl.use_strict",
+	DefineCustomBoolVariable("plperl.use_strict",
 	  "If true, will compile trusted and untrusted perl code in strict mode",
 							 NULL,
 							 &plperl_use_strict,
@@ -154,19 +157,8 @@ plperl_init(void)
 	EmitWarningsOnPlaceholders("plperl");
 
 	plperl_init_interp();
-	plperl_firstcall = false;
-}
-
-
-/* Perform initialization during backend startup. */
 
-static void
-plperl_init_all(void)
-{
-	if (plperl_firstcall)
-		plperl_init();
-
-	/* We don't need to do anything yet when a new backend starts. */
+	inited = true;
 }
 
 /* Each of these macros must represent a single string literal */
@@ -657,8 +649,6 @@ plperl_call_handler(PG_FUNCTION_ARGS)
 	Datum		retval;
 	plperl_call_data *save_call_data;
 
-	plperl_init_all();
-
 	save_call_data = current_call_data;
 	PG_TRY();
 	{
@@ -741,11 +731,7 @@ plperl_validator(PG_FUNCTION_ARGS)
 	/* Postpone body checks if !check_function_bodies */
 	if (check_function_bodies)
 	{
-		plperl_proc_desc *prodesc;
-
-		plperl_init_all();
-
-		prodesc = compile_plperl_function(funcoid, istrigger);
+		(void) compile_plperl_function(funcoid, istrigger);
 	}
 
 	/* the result of a validator is ignored */
diff --git a/src/pl/plpgsql/src/pl_handler.c b/src/pl/plpgsql/src/pl_handler.c
index d8eb22f995e..22264f5a283 100644
--- a/src/pl/plpgsql/src/pl_handler.c
+++ b/src/pl/plpgsql/src/pl_handler.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_handler.c,v 1.29 2006/05/30 22:12:16 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_handler.c,v 1.30 2006/08/08 19:15:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -28,41 +28,25 @@ extern DLLIMPORT bool check_function_bodies;
 
 PG_MODULE_MAGIC;
 
-static bool plpgsql_firstcall = true;
-
-static void plpgsql_init_all(void);
-
 
 /*
- * plpgsql_init()			- postmaster-startup safe initialization
+ * _PG_init()			- library load-time initialization
  *
- * DO NOT make this static --- it has to be callable by preload
+ * DO NOT make this static nor change its name!
  */
 void
-plpgsql_init(void)
+_PG_init(void)
 {
-	/* Do initialization only once */
-	if (!plpgsql_firstcall)
+	/* Be sure we do initialization only once (should be redundant now) */
+	static bool inited = false;
+
+	if (inited)
 		return;
 
 	plpgsql_HashTableInit();
 	RegisterXactCallback(plpgsql_xact_cb, NULL);
-	plpgsql_firstcall = false;
-}
-
-/*
- * plpgsql_init_all()		- Initialize all
- */
-static void
-plpgsql_init_all(void)
-{
-	/* Execute any postmaster-startup safe initialization */
-	plpgsql_init();
 
-	/*
-	 * Any other initialization that must be done each time a new backend
-	 * starts -- currently none
-	 */
+	inited = true;
 }
 
 /* ----------
@@ -81,9 +65,6 @@ plpgsql_call_handler(PG_FUNCTION_ARGS)
 	Datum		retval;
 	int			rc;
 
-	/* perform initialization */
-	plpgsql_init_all();
-
 	/*
 	 * Connect to SPI manager
 	 */
@@ -135,9 +116,6 @@ plpgsql_validator(PG_FUNCTION_ARGS)
 	bool		istrigger = false;
 	int			i;
 
-	/* perform initialization */
-	plpgsql_init_all();
-
 	/* Get the new function's pg_proc entry */
 	tuple = SearchSysCache(PROCOID,
 						   ObjectIdGetDatum(funcoid),
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index 32d7fbaf696..268fc13821e 100644
--- a/src/pl/plpgsql/src/plpgsql.h
+++ b/src/pl/plpgsql/src/plpgsql.h
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.77 2006/07/11 17:26:59 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.78 2006/08/08 19:15:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -678,7 +678,7 @@ extern void plpgsql_compile_error_callback(void *arg);
  * Functions in pl_handler.c
  * ----------
  */
-extern void plpgsql_init(void);
+extern void _PG_init(void);
 extern Datum plpgsql_call_handler(PG_FUNCTION_ARGS);
 extern Datum plpgsql_validator(PG_FUNCTION_ARGS);
 
diff --git a/src/pl/plpython/plpython.c b/src/pl/plpython/plpython.c
index 164df875a5a..289ab2e7b73 100644
--- a/src/pl/plpython/plpython.c
+++ b/src/pl/plpython/plpython.c
@@ -1,7 +1,7 @@
 /**********************************************************************
  * plpython.c - python as a procedural language for PostgreSQL
  *
- *	$PostgreSQL: pgsql/src/pl/plpython/plpython.c,v 1.84 2006/07/06 01:55:51 momjian Exp $
+ *	$PostgreSQL: pgsql/src/pl/plpython/plpython.c,v 1.85 2006/08/08 19:15:09 tgl Exp $
  *
  *********************************************************************
  */
@@ -155,11 +155,11 @@ typedef struct PLyResultObject
 /* function declarations */
 
 /* Two exported functions: first is the magic telling Postgresql
- * what function call interface it implements. Second allows
- * preinitialization of the interpreter during postmaster startup.
+ * what function call interface it implements. Second is for
+ * initialization of the interpreter during library load.
  */
 Datum		plpython_call_handler(PG_FUNCTION_ARGS);
-void		plpython_init(void);
+void		_PG_init(void);
 
 PG_FUNCTION_INFO_V1(plpython_call_handler);
 
@@ -169,7 +169,6 @@ PG_FUNCTION_INFO_V1(plpython_call_handler);
  * of plpython_call_handler.  initialize the python interpreter
  * and global data.
  */
-static void PLy_init_all(void);
 static void PLy_init_interp(void);
 static void PLy_init_plpy(void);
 
@@ -233,9 +232,6 @@ static PyObject *PLyLong_FromString(const char *);
 static PyObject *PLyString_FromString(const char *);
 
 
-/* global data */
-static bool	PLy_first_call = true;
-
 /*
  * Currently active plpython function
  */
@@ -301,8 +297,6 @@ plpython_call_handler(PG_FUNCTION_ARGS)
 	PLyProcedure *save_curr_proc;
 	PLyProcedure *volatile proc = NULL;
 
-	PLy_init_all();
-
 	if (SPI_connect() != SPI_OK_CONNECT)
 		elog(ERROR, "could not connect to SPI manager");
 
@@ -2263,25 +2257,19 @@ PLy_spi_execute_fetch_result(SPITupleTable *tuptable, int rows, int status)
  */
 
 /*
- * plpython_init()			- Initialize everything that can be
- *							  safely initialized during postmaster
- *							  startup.
+ * _PG_init()			- library load-time initialization
  *
- * DO NOT make this static --- it has to be callable by preload
+ * DO NOT make this static nor change its name!
  */
 void
-plpython_init(void)
+_PG_init(void)
 {
-	static volatile bool init_active = false;
+	/* Be sure we do initialization only once (should be redundant now) */
+	static bool inited = false;
 
-	/* Do initialization only once */
-	if (!PLy_first_call)
+	if (inited)
 		return;
 
-	if (init_active)
-		elog(FATAL, "initialization of language module failed");
-	init_active = true;
-
 	Py_Initialize();
 	PLy_init_interp();
 	PLy_init_plpy();
@@ -2291,20 +2279,7 @@ plpython_init(void)
 	if (PLy_procedure_cache == NULL)
 		PLy_elog(ERROR, "could not create procedure cache");
 
-	PLy_first_call = false;
-}
-
-static void
-PLy_init_all(void)
-{
-	/* Execute postmaster-startup safe initialization */
-	if (PLy_first_call)
-		plpython_init();
-
-	/*
-	 * Any other initialization that must be done each time a new backend
-	 * starts -- currently none
-	 */
+	inited = true;
 }
 
 static void
diff --git a/src/pl/tcl/pltcl.c b/src/pl/tcl/pltcl.c
index 75964b25684..54abd096722 100644
--- a/src/pl/tcl/pltcl.c
+++ b/src/pl/tcl/pltcl.c
@@ -2,7 +2,7 @@
  * pltcl.c		- PostgreSQL support for Tcl as
  *				  procedural language (PL)
  *
- *	  $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.105 2006/06/16 18:42:24 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/tcl/pltcl.c,v 1.106 2006/08/08 19:15:09 tgl Exp $
  *
  **********************************************************************/
 
@@ -120,15 +120,14 @@ static pltcl_proc_desc *pltcl_current_prodesc = NULL;
 /**********************************************************************
  * Forward declarations
  **********************************************************************/
+Datum		pltcl_call_handler(PG_FUNCTION_ARGS);
+Datum		pltclu_call_handler(PG_FUNCTION_ARGS);
+void		_PG_init(void);
+
 static void pltcl_init_all(void);
 static void pltcl_init_interp(Tcl_Interp *interp);
-
 static void pltcl_init_load_unknown(Tcl_Interp *interp);
 
-Datum		pltcl_call_handler(PG_FUNCTION_ARGS);
-Datum		pltclu_call_handler(PG_FUNCTION_ARGS);
-void		pltcl_init(void);
-
 static Datum pltcl_func_handler(PG_FUNCTION_ARGS);
 
 static HeapTuple pltcl_trigger_handler(PG_FUNCTION_ARGS);
@@ -182,17 +181,15 @@ perm_fmgr_info(Oid functionId, FmgrInfo *finfo)
 	fmgr_info_cxt(functionId, finfo, TopMemoryContext);
 }
 
-/**********************************************************************
- * pltcl_init()		- Initialize all that's safe to do in the postmaster
+/*
+ * _PG_init()			- library load-time initialization
  *
- * DO NOT make this static --- it has to be callable by preload
- **********************************************************************/
+ * DO NOT make this static nor change its name!
+ */
 void
-pltcl_init(void)
+_PG_init(void)
 {
-	/************************************************************
-	 * Do initialization only once
-	 ************************************************************/
+	/* Be sure we do initialization only once (should be redundant now) */
 	if (pltcl_pm_init_done)
 		return;
 
@@ -236,20 +233,15 @@ pltcl_init(void)
 
 /**********************************************************************
  * pltcl_init_all()		- Initialize all
+ *
+ * This does initialization that can't be done in the postmaster, and
+ * hence is not safe to do at library load time.
  **********************************************************************/
 static void
 pltcl_init_all(void)
 {
 	/************************************************************
-	 * Execute postmaster-startup safe initialization
-	 ************************************************************/
-	if (!pltcl_pm_init_done)
-		pltcl_init();
-
-	/************************************************************
-	 * Any other initialization that must be done each time a new
-	 * backend starts:
-	 * - Try to load the unknown procedure from pltcl_modules
+	 * Try to load the unknown procedure from pltcl_modules
 	 ************************************************************/
 	if (!pltcl_be_init_done)
 	{