Create the catalog infrastructure for foreign-data-wrapper handlers.

Add a fdwhandler column to pg_foreign_data_wrapper, plus HANDLER options
in the CREATE FOREIGN DATA WRAPPER and ALTER FOREIGN DATA WRAPPER commands,
plus pg_dump support for same.  Also invent a new pseudotype fdw_handler
with properties similar to language_handler.

This is split out of the "FDW API" patch for ease of review; it's all stuff
we will certainly need, regardless of any other details of the FDW API.
FDW handler functions will not actually get called yet.

In passing, fix some omissions and infelicities in foreigncmds.c.

Shigeru Hanada, Jan Urbanski, Heikki Linnakangas

3 files changed, 42 insertions, 15 deletions

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 60609b6b359..a9fa3357e79 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -6260,6 +6260,7 @@ getForeignDataWrappers(int *numForeignDataWrappers)
 	int			i_oid;
 	int			i_fdwname;
 	int			i_rolname;
+	int			i_fdwhandler;
 	int			i_fdwvalidator;
 	int			i_fdwacl;
 	int			i_fdwoptions;
@@ -6274,13 +6275,30 @@ getForeignDataWrappers(int *numForeignDataWrappers)
 	/* Make sure we are in proper schema */
 	selectSourceSchema("pg_catalog");
 
-	appendPQExpBuffer(query, "SELECT tableoid, oid, fdwname, "
-		"(%s fdwowner) AS rolname, fdwvalidator::pg_catalog.regproc, fdwacl,"
-					  "array_to_string(ARRAY("
-		 "		SELECT option_name || ' ' || quote_literal(option_value) "
-	   "		FROM pg_options_to_table(fdwoptions)), ', ') AS fdwoptions "
-					  "FROM pg_foreign_data_wrapper",
-					  username_subquery);
+	if (g_fout->remoteVersion >= 90100)
+	{
+		appendPQExpBuffer(query, "SELECT tableoid, oid, fdwname, "
+						  "(%s fdwowner) AS rolname, "
+						  "fdwhandler::pg_catalog.regproc, "
+						  "fdwvalidator::pg_catalog.regproc, fdwacl, "
+						  "array_to_string(ARRAY("
+						  "		SELECT option_name || ' ' || quote_literal(option_value) "
+						  "		FROM pg_options_to_table(fdwoptions)), ', ') AS fdwoptions "
+						  "FROM pg_foreign_data_wrapper",
+						  username_subquery);
+	}
+	else
+	{
+		appendPQExpBuffer(query, "SELECT tableoid, oid, fdwname, "
+						  "(%s fdwowner) AS rolname, "
+						  "'-' AS fdwhandler, "
+						  "fdwvalidator::pg_catalog.regproc, fdwacl, "
+						  "array_to_string(ARRAY("
+						  "		SELECT option_name || ' ' || quote_literal(option_value) "
+						  "		FROM pg_options_to_table(fdwoptions)), ', ') AS fdwoptions "
+						  "FROM pg_foreign_data_wrapper",
+						  username_subquery);
+	}
 
 	res = PQexec(g_conn, query->data);
 	check_sql_result(res, g_conn, query->data, PGRES_TUPLES_OK);
@@ -6294,6 +6312,7 @@ getForeignDataWrappers(int *numForeignDataWrappers)
 	i_oid = PQfnumber(res, "oid");
 	i_fdwname = PQfnumber(res, "fdwname");
 	i_rolname = PQfnumber(res, "rolname");
+	i_fdwhandler = PQfnumber(res, "fdwhandler");
 	i_fdwvalidator = PQfnumber(res, "fdwvalidator");
 	i_fdwacl = PQfnumber(res, "fdwacl");
 	i_fdwoptions = PQfnumber(res, "fdwoptions");
@@ -6307,11 +6326,11 @@ getForeignDataWrappers(int *numForeignDataWrappers)
 		fdwinfo[i].dobj.name = strdup(PQgetvalue(res, i, i_fdwname));
 		fdwinfo[i].dobj.namespace = NULL;
 		fdwinfo[i].rolname = strdup(PQgetvalue(res, i, i_rolname));
+		fdwinfo[i].fdwhandler = strdup(PQgetvalue(res, i, i_fdwhandler));
 		fdwinfo[i].fdwvalidator = strdup(PQgetvalue(res, i, i_fdwvalidator));
 		fdwinfo[i].fdwoptions = strdup(PQgetvalue(res, i, i_fdwoptions));
 		fdwinfo[i].fdwacl = strdup(PQgetvalue(res, i, i_fdwacl));
 
-
 		/* Decide whether we want to dump it */
 		selectDumpableObject(&(fdwinfo[i].dobj));
 	}
@@ -10929,11 +10948,13 @@ dumpForeignDataWrapper(Archive *fout, FdwInfo *fdwinfo)
 	appendPQExpBuffer(q, "CREATE FOREIGN DATA WRAPPER %s",
 					  qfdwname);
 
-	if (fdwinfo->fdwvalidator && strcmp(fdwinfo->fdwvalidator, "-") != 0)
-		appendPQExpBuffer(q, " VALIDATOR %s",
-						  fdwinfo->fdwvalidator);
+	if (strcmp(fdwinfo->fdwhandler, "-") != 0)
+		appendPQExpBuffer(q, " HANDLER %s", fdwinfo->fdwhandler);
+
+	if (strcmp(fdwinfo->fdwvalidator, "-") != 0)
+		appendPQExpBuffer(q, " VALIDATOR %s", fdwinfo->fdwvalidator);
 
-	if (fdwinfo->fdwoptions && strlen(fdwinfo->fdwoptions) > 0)
+	if (strlen(fdwinfo->fdwoptions) > 0)
 		appendPQExpBuffer(q, " OPTIONS (%s)", fdwinfo->fdwoptions);
 
 	appendPQExpBuffer(q, ";\n");
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 3c02af44b13..94b7a6bf928 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -440,6 +440,7 @@ typedef struct _fdwInfo
 {
 	DumpableObject dobj;
 	char	   *rolname;
+	char	   *fdwhandler;
 	char	   *fdwvalidator;
 	char	   *fdwoptions;
 	char	   *fdwacl;
diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index 735eef786b4..94396b19106 100644
--- a/src/bin/psql/describe.c
+++ b/src/bin/psql/describe.c
@@ -3562,10 +3562,15 @@ listForeignDataWrappers(const char *pattern, bool verbose)
 	initPQExpBuffer(&buf);
 	printfPQExpBuffer(&buf,
 					  "SELECT fdwname AS \"%s\",\n"
-					  "  pg_catalog.pg_get_userbyid(fdwowner) AS \"%s\",\n"
-					  "  fdwvalidator::pg_catalog.regproc AS \"%s\"",
+					  "  pg_catalog.pg_get_userbyid(fdwowner) AS \"%s\",\n",
 					  gettext_noop("Name"),
-					  gettext_noop("Owner"),
+					  gettext_noop("Owner"));
+	if (pset.sversion >= 90100)
+		appendPQExpBuffer(&buf,
+						  "  fdwhandler::pg_catalog.regproc AS \"%s\",\n",
+						  gettext_noop("Handler"));
+	appendPQExpBuffer(&buf,
+					  "  fdwvalidator::pg_catalog.regproc AS \"%s\"",
 					  gettext_noop("Validator"));
 
 	if (verbose)