Rearrange extension-related views as per recent discussion.

The original design of pg_available_extensions did not consider the
possibility of version-specific control files.  Split it into two views:
pg_available_extensions shows information that is generic about an
extension, while pg_available_extension_versions shows all available
versions together with information that could be version-dependent.
Also, add an SRF pg_extension_update_paths() to assist in checking that
a collection of update scripts provide sane update path sequences.

doc/src/sgml/catalogs.sgml

@@ -6330,6 +6330,11 @@
       <entry>available extensions</entry>
      </row>
 
+     <row>
+      <entry><link linkend="view-pg-available-extension-versions"><structname>pg_available_extension_versions</structname></link></entry>
+      <entry>available versions of extensions</entry>
+     </row>
+
      <row>
       <entry><link linkend="view-pg-cursors"><structname>pg_cursors</structname></link></entry>
       <entry>open cursors</entry>
@@ -6460,31 +6465,19 @@
      </row>
 
      <row>
-      <entry><structfield>version</structfield></entry>
+      <entry><structfield>default_version</structfield></entry>
       <entry><type>text</type></entry>
-      <entry>Version string from the extension's control file</entry>
+      <entry>Name of default version, or <literal>NULL</literal> if none is
+       specified</entry>
      </row>
 
      <row>
-      <entry><structfield>installed</structfield></entry>
+      <entry><structfield>installed_version</structfield></entry>
       <entry><type>text</type></entry>
       <entry>Currently installed version of the extension,
        or <literal>NULL</literal> if not installed</entry>
      </row>
 
-     <row>
-      <entry><structfield>schema</structfield></entry>
-      <entry><type>name</type></entry>
-      <entry>Name of the schema where the extension is installed,
-       or <literal>NULL</literal> if not installed</entry>
-     </row>
-
-     <row>
-      <entry><structfield>relocatable</structfield></entry>
-      <entry><type>bool</type></entry>
-      <entry>True if extension can be relocated to another schema</entry>
-     </row>
-
      <row>
       <entry><structfield>comment</structfield></entry>
       <entry><type>text</type></entry>
@@ -6497,7 +6490,88 @@
   <para>
    The <structname>pg_available_extensions</structname> view is read only.
   </para>
+ </sect1>
 
+ <sect1 id="view-pg-available-extension-versions">
+  <title><structname>pg_available_extension_versions</structname></title>
+
+  <indexterm zone="view-pg-available-extension-versions">
+   <primary>pg_available_extension_versions</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_available_extension_versions</structname> view lists the
+   specific extension versions that are available for installation.  This view
+   can only be read by superusers.  See also the <link
+   linkend="catalog-pg-extension"><structname>pg_extension</structname></link>
+   catalog, which shows the extensions currently installed.
+  </para>
+
+  <table>
+   <title><structname>pg_available_extension_versions</> Columns</title>
+
+   <tgroup cols="3">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry><structfield>name</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry>Extension name</entry>
+     </row>
+
+     <row>
+      <entry><structfield>version</structfield></entry>
+      <entry><type>text</type></entry>
+      <entry>Version name</entry>
+     </row>
+
+     <row>
+      <entry><structfield>installed</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry>True if this version of this extension is currently
+       installed</entry>
+     </row>
+
+     <row>
+      <entry><structfield>relocatable</structfield></entry>
+      <entry><type>bool</type></entry>
+      <entry>True if extension can be relocated to another schema</entry>
+     </row>
+
+     <row>
+      <entry><structfield>schema</structfield></entry>
+      <entry><type>name</type></entry>
+      <entry>Name of the schema that the extension must be installed into,
+       or <literal>NULL</literal> if partially or fully relocatable</entry>
+     </row>
+
+     <row>
+      <entry><structfield>requires</structfield></entry>
+      <entry><type>name[]</type></entry>
+      <entry>Names of prerequisite extensions,
+       or <literal>NULL</literal> if none</entry>
+     </row>
+
+     <row>
+      <entry><structfield>comment</structfield></entry>
+      <entry><type>text</type></entry>
+      <entry>Comment string from the extension's control file</entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+  <para>
+   The <structname>pg_available_extension_versions</structname> view is read
+   only.
+  </para>
  </sect1>
 
  <sect1 id="view-pg-cursors">

doc/src/sgml/extend.sgml

@@ -765,6 +765,20 @@ SELECT pg_catalog.pg_extension_config_dump('my_config', 'WHERE NOT standard_entr
      path than to move ahead one version at a time.  If the downgrade script
      drops any irreplaceable objects, this will yield undesirable results.
     </para>
+
+    <para>
+     To check for unexpected update paths, use this command:
+<programlisting>
+SELECT * FROM pg_extension_update_paths('<replaceable>extension_name</>');
+</programlisting>
+     This shows each pair of distinct known version names for the specified
+     extension, together with the update path sequence that would be taken to
+     get from the source version to the target version, or <literal>NULL</> if
+     there is no available update path.  The path is shown in textual form
+     with <literal>--</> separators.  You can use
+     <literal>regexp_split_to_array(path,'--')</> if you prefer an array
+     format.
+    </para>
    </sect2>
 
    <sect2>

src/backend/catalog/system_views.sql

@@ -154,11 +154,17 @@ CREATE VIEW pg_cursors AS
     SELECT * FROM pg_cursor() AS C;
 
 CREATE VIEW pg_available_extensions AS
-    SELECT E.name, E.version, X.extversion AS installed,
+    SELECT E.name, E.default_version, X.extversion AS installed_version,
-           N.nspname AS schema, E.relocatable, E.comment
+           E.comment
       FROM pg_available_extensions() AS E
-           LEFT JOIN pg_extension AS X ON E.name = X.extname
+           LEFT JOIN pg_extension AS X ON E.name = X.extname;
-           LEFT JOIN pg_namespace AS N on N.oid = X.extnamespace;
+
+CREATE VIEW pg_available_extension_versions AS
+    SELECT E.name, E.version, (X.extname IS NOT NULL) AS installed,
+           E.relocatable, E.schema, E.requires, E.comment
+      FROM pg_available_extension_versions() AS E
+           LEFT JOIN pg_extension AS X
+             ON E.name = X.extname AND E.version = X.extversion;
 
 CREATE VIEW pg_prepared_xacts AS
     SELECT P.transaction, P.gid, P.prepared,

src/backend/commands/extension.c

@@ -24,6 +24,7 @@
 #include "postgres.h"
 
 #include <dirent.h>
+#include <limits.h>
 #include <unistd.h>
 
 #include "access/sysattr.h"
@@ -80,6 +81,7 @@ typedef struct ExtensionVersionInfo
 {
 	char	   *name;			/* name of the starting version */
 	List	   *reachable;		/* List of ExtensionVersionInfo's */
+	bool		installable;	/* does this version have an install script? */
 	/* working state for Dijkstra's algorithm: */
 	bool		distance_known;	/* is distance from start known yet? */
 	int			distance;		/* current worst-case distance estimate */
@@ -87,6 +89,13 @@ typedef struct ExtensionVersionInfo
 } ExtensionVersionInfo;
 
 /* Local functions */
+static List *find_update_path(List *evi_list,
+				 ExtensionVersionInfo *evi_start,
+				 ExtensionVersionInfo *evi_target,
+				 bool reinitialize);
+static void get_available_versions_for_extension(ExtensionControlFile *pcontrol,
+									 Tuplestorestate *tupstore,
+									 TupleDesc tupdesc);
 static void ApplyExtensionUpdates(Oid extensionOid,
 					  ExtensionControlFile *pcontrol,
 					  const char *initialVersion,
@@ -909,6 +918,7 @@ get_ext_ver_info(const char *versionname, List **evi_list)
 	evi = (ExtensionVersionInfo *) palloc(sizeof(ExtensionVersionInfo));
 	evi->name = pstrdup(versionname);
 	evi->reachable = NIL;
+	evi->installable = false;
 	/* initialize for later application of Dijkstra's algorithm */
 	evi->distance_known = false;
 	evi->distance = INT_MAX;
@@ -981,15 +991,24 @@ get_ext_ver_list(ExtensionControlFile *control)
 			de->d_name[extnamelen + 1] != '-')
 			continue;
 
-		/* extract version names from 'extname--something.sql' filename */
+		/* extract version name(s) from 'extname--something.sql' filename */
 		vername = pstrdup(de->d_name + extnamelen + 2);
 		*strrchr(vername, '.') = '\0';
 		vername2 = strstr(vername, "--");
 		if (!vername2)
-			continue;			/* it's not an update script */
+		{
+			/* It's an install, not update, script; record its version name */
+			evi = get_ext_ver_info(vername, &evi_list);
+			evi->installable = true;
+			continue;
+		}
 		*vername2 = '\0';		/* terminate first version */
 		vername2 += 2;			/* and point to second */
 
+		/* if there's a third --, it's bogus, ignore it */
+		if (strstr(vername2, "--"))
+			continue;
+
 		/* Create ExtensionVersionInfos and link them together */
 		evi = get_ext_ver_info(vername, &evi_list);
 		evi2 = get_ext_ver_info(vername2, &evi_list);
@@ -1015,7 +1034,6 @@ identify_update_path(ExtensionControlFile *control,
 	List	   *evi_list;
 	ExtensionVersionInfo *evi_start;
 	ExtensionVersionInfo *evi_target;
-	ExtensionVersionInfo *evi;
 
 	if (strcmp(oldVersion, newVersion) == 0)
 		ereport(ERROR,
@@ -1029,12 +1047,57 @@ identify_update_path(ExtensionControlFile *control,
 	evi_start = get_ext_ver_info(oldVersion, &evi_list);
 	evi_target = get_ext_ver_info(newVersion, &evi_list);
 
+	/* Find shortest path */
+	result = find_update_path(evi_list, evi_start, evi_target, false);
+
+	if (result == NIL)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("extension \"%s\" has no update path from version \"%s\" to version \"%s\"",
+						control->name, oldVersion, newVersion)));
+
+	return result;
+}
+
+/*
+ * Apply Dijkstra's algorithm to find the shortest path from evi_start to
+ * evi_target.
+ *
+ * If reinitialize is false, assume the ExtensionVersionInfo list has not
+ * been used for this before, and the initialization done by get_ext_ver_info
+ * is still good.
+ *
+ * Result is a List of names of versions to transition through (the initial
+ * version is *not* included).  Returns NIL if no such path.
+ */
+static List *
+find_update_path(List *evi_list,
+				 ExtensionVersionInfo *evi_start,
+				 ExtensionVersionInfo *evi_target,
+				 bool reinitialize)
+{
+	List	   *result;
+	ExtensionVersionInfo *evi;
+	ListCell   *lc;
+
+	/* Caller error if start == target */
+	Assert(evi_start != evi_target);
+
+	if (reinitialize)
+	{
+		foreach(lc, evi_list)
+		{
+			evi = (ExtensionVersionInfo *) lfirst(lc);
+			evi->distance_known = false;
+			evi->distance = INT_MAX;
+			evi->previous = NULL;
+		}
+	}
+
 	evi_start->distance = 0;
 
 	while ((evi = get_nearest_unprocessed_vertex(evi_list)) != NULL)
 	{
-		ListCell   *lc;
-
 		if (evi->distance == INT_MAX)
 			break;				/* all remaining vertices are unreachable */
 		evi->distance_known = true;
@@ -1068,11 +1131,9 @@ identify_update_path(ExtensionControlFile *control,
 		}
 	}
 
+	/* Return NIL if target is not reachable from start */
 	if (!evi_target->distance_known)
-		ereport(ERROR,
+		return NIL;
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("extension \"%s\" has no update path from version \"%s\" to version \"%s\"",
-						control->name, oldVersion, newVersion)));
 
 	/* Build and return list of version names representing the update path */
 	result = NIL;
@@ -1553,9 +1614,9 @@ RemoveExtensionById(Oid extId)
 }
 
 /*
- * This function lists the extensions available in the control directory
+ * This function lists the available extensions (one row per primary control
- * (each of which might or might not actually be installed).  We parse each
+ * file in the control directory).  We parse each control file and report the
- * available control file and report the interesting fields.
+ * interesting fields.
  *
  * The system view pg_available_extensions provides a user interface to this
  * SRF, adding information about whether the extensions are installed in the
@@ -1593,6 +1654,7 @@ pg_available_extensions(PG_FUNCTION_ARGS)
 	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
 		elog(ERROR, "return type must be a row type");
 
+	/* Build tuplestore to hold the result rows */
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
 
@@ -1620,8 +1682,8 @@ pg_available_extensions(PG_FUNCTION_ARGS)
 		{
 			ExtensionControlFile *control;
 			char	   *extname;
-			Datum		values[4];
+			Datum		values[3];
-			bool		nulls[4];
+			bool		nulls[3];
 
 			if (!is_extension_control_filename(de->d_name))
 				continue;
@@ -1647,13 +1709,11 @@ pg_available_extensions(PG_FUNCTION_ARGS)
 				nulls[1] = true;
 			else
 				values[1] = CStringGetTextDatum(control->default_version);
-			/* relocatable */
-			values[2] = BoolGetDatum(control->relocatable);
 			/* comment */
 			if (control->comment == NULL)
-				nulls[3] = true;
+				nulls[2] = true;
 			else
-				values[3] = CStringGetTextDatum(control->comment);
+				values[2] = CStringGetTextDatum(control->comment);
 
 			tuplestore_putvalues(tupstore, tupdesc, values, nulls);
 		}
@@ -1667,6 +1727,319 @@ pg_available_extensions(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * This function lists the available extension versions (one row per
+ * extension installation script).  For each version, we parse the related
+ * control file(s) and report the interesting fields.
+ *
+ * The system view pg_available_extension_versions provides a user interface
+ * to this SRF, adding information about which versions are installed in the
+ * current DB.
+ */
+Datum
+pg_available_extension_versions(PG_FUNCTION_ARGS)
+{
+	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	TupleDesc			tupdesc;
+	Tuplestorestate	   *tupstore;
+	MemoryContext		per_query_ctx;
+	MemoryContext		oldcontext;
+	char			   *location;
+	DIR				   *dir;
+	struct dirent	   *de;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 (errmsg("must be superuser to list available extensions"))));
+
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not " \
+						"allowed in this context")));
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	/* Build tuplestore to hold the result rows */
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = tupdesc;
+
+	MemoryContextSwitchTo(oldcontext);
+
+	location = get_extension_control_directory();
+	dir  = AllocateDir(location);
+
+	/*
+	 * If the control directory doesn't exist, we want to silently return
+	 * an empty set.  Any other error will be reported by ReadDir.
+	 */
+	if (dir == NULL && errno == ENOENT)
+	{
+		/* do nothing */
+	}
+	else
+	{
+		while ((de = ReadDir(dir, location)) != NULL)
+		{
+			ExtensionControlFile *control;
+			char	   *extname;
+
+			if (!is_extension_control_filename(de->d_name))
+				continue;
+
+			/* extract extension name from 'name.control' filename */
+			extname = pstrdup(de->d_name);
+			*strrchr(extname, '.') = '\0';
+
+			/* ignore it if it's an auxiliary control file */
+			if (strstr(extname, "--"))
+				continue;
+
+			/* read the control file */
+			control = read_extension_control_file(extname);
+
+			/* scan extension's script directory for install scripts */
+			get_available_versions_for_extension(control, tupstore, tupdesc);
+		}
+
+		FreeDir(dir);
+	}
+
+	/* clean up and return the tuplestore */
+	tuplestore_donestoring(tupstore);
+
+	return (Datum) 0;
+}
+
+/*
+ * Inner loop for pg_available_extension_versions:
+ *		read versions of one extension, add rows to tupstore
+ */
+static void
+get_available_versions_for_extension(ExtensionControlFile *pcontrol,
+									 Tuplestorestate *tupstore,
+									 TupleDesc tupdesc)
+{
+	int			extnamelen = strlen(pcontrol->name);
+	char	   *location;
+	DIR		   *dir;
+	struct dirent *de;
+
+	location = get_extension_script_directory(pcontrol);
+	dir  = AllocateDir(location);
+	/* Note this will fail if script directory doesn't exist */
+	while ((de = ReadDir(dir, location)) != NULL)
+	{
+		ExtensionControlFile *control;
+		char	   *vername;
+		Datum		values[6];
+		bool		nulls[6];
+
+		/* must be a .sql file ... */
+		if (!is_extension_script_filename(de->d_name))
+			continue;
+
+		/* ... matching extension name followed by separator */
+		if (strncmp(de->d_name, pcontrol->name, extnamelen) != 0 ||
+			de->d_name[extnamelen] != '-' ||
+			de->d_name[extnamelen + 1] != '-')
+			continue;
+
+		/* extract version name from 'extname--something.sql' filename */
+		vername = pstrdup(de->d_name + extnamelen + 2);
+		*strrchr(vername, '.') = '\0';
+
+		/* ignore it if it's an update script */
+		if (strstr(vername, "--"))
+			continue;
+
+		/*
+		 * Fetch parameters for specific version (pcontrol is not changed)
+		 */
+		control = read_extension_aux_control_file(pcontrol, vername);
+
+		memset(values, 0, sizeof(values));
+		memset(nulls, 0, sizeof(nulls));
+
+		/* name */
+		values[0] = DirectFunctionCall1(namein,
+										CStringGetDatum(control->name));
+		/* version */
+		values[1] = CStringGetTextDatum(vername);
+		/* relocatable */
+		values[2] = BoolGetDatum(control->relocatable);
+		/* schema */
+		if (control->schema == NULL)
+			nulls[3] = true;
+		else
+			values[3] = DirectFunctionCall1(namein,
+											CStringGetDatum(control->schema));
+		/* requires */
+		if (control->requires == NIL)
+			nulls[4] = true;
+		else
+		{
+			Datum	   *datums;
+			int			ndatums;
+			ArrayType  *a;
+			ListCell   *lc;
+
+			ndatums = list_length(control->requires);
+			datums = (Datum *) palloc(ndatums * sizeof(Datum));
+			ndatums = 0;
+			foreach(lc, control->requires)
+			{
+				char	   *curreq = (char *) lfirst(lc);
+
+				datums[ndatums++] =
+					DirectFunctionCall1(namein, CStringGetDatum(curreq));
+			}
+			a = construct_array(datums, ndatums,
+								NAMEOID,
+								NAMEDATALEN, false, 'c');
+			values[4] = PointerGetDatum(a);
+		}
+		/* comment */
+		if (control->comment == NULL)
+			nulls[5] = true;
+		else
+			values[5] = CStringGetTextDatum(control->comment);
+
+		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+	}
+
+	FreeDir(dir);
+}
+
+/*
+ * This function reports the version update paths that exist for the
+ * specified extension.
+ */
+Datum
+pg_extension_update_paths(PG_FUNCTION_ARGS)
+{
+	Name		extname = PG_GETARG_NAME(0);
+	ReturnSetInfo	   *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	TupleDesc			tupdesc;
+	Tuplestorestate	   *tupstore;
+	MemoryContext		per_query_ctx;
+	MemoryContext		oldcontext;
+	List	   *evi_list;
+	ExtensionControlFile *control;
+	ListCell   *lc1;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 (errmsg("must be superuser to list extension update paths"))));
+
+	/* Check extension name validity before any filesystem access */
+	check_valid_extension_name(NameStr(*extname));
+
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsinfo->allowedModes & SFRM_Materialize))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not " \
+						"allowed in this context")));
+
+	/* Build a tuple descriptor for our result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	/* Build tuplestore to hold the result rows */
+	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+	oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+	tupstore = tuplestore_begin_heap(true, false, work_mem);
+	rsinfo->returnMode = SFRM_Materialize;
+	rsinfo->setResult = tupstore;
+	rsinfo->setDesc = tupdesc;
+
+	MemoryContextSwitchTo(oldcontext);
+
+	/* Read the extension's control file */
+	control = read_extension_control_file(NameStr(*extname));
+
+	/* Extract the version update graph from the script directory */
+	evi_list = get_ext_ver_list(control);
+
+	/* Iterate over all pairs of versions */
+	foreach(lc1, evi_list)
+	{
+		ExtensionVersionInfo *evi1 = (ExtensionVersionInfo *) lfirst(lc1);
+		ListCell   *lc2;
+
+		foreach(lc2, evi_list)
+		{
+			ExtensionVersionInfo *evi2 = (ExtensionVersionInfo *) lfirst(lc2);
+			List	   *path;
+			Datum		values[3];
+			bool		nulls[3];
+
+			if (evi1 == evi2)
+				continue;
+
+			/* Find shortest path from evi1 to evi2 */
+			path = find_update_path(evi_list, evi1, evi2, true);
+
+			/* Emit result row */
+			memset(values, 0, sizeof(values));
+			memset(nulls, 0, sizeof(nulls));
+
+			/* source */
+			values[0] = CStringGetTextDatum(evi1->name);
+			/* target */
+			values[1] = CStringGetTextDatum(evi2->name);
+			/* path */
+			if (path == NIL)
+				nulls[2] = true;
+			else
+			{
+				StringInfoData pathbuf;
+				ListCell   *lcv;
+
+				initStringInfo(&pathbuf);
+				/* The path doesn't include start vertex, but show it */
+				appendStringInfoString(&pathbuf, evi1->name);
+				foreach(lcv, path)
+				{
+					char	   *versionName = (char *) lfirst(lcv);
+
+					appendStringInfoString(&pathbuf, "--");
+					appendStringInfoString(&pathbuf, versionName);
+				}
+				values[2] = CStringGetTextDatum(pathbuf.data);
+				pfree(pathbuf.data);
+			}
+
+			tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+		}
+	}
+
+	/* clean up and return the tuplestore */
+	tuplestore_donestoring(tupstore);
+
+	return (Datum) 0;
+}
+
 /*
  * pg_extension_config_dump
  *

src/bin/psql/tab-complete.c

@@ -586,7 +586,7 @@ static const SchemaQuery Query_for_list_of_views = {
 #define Query_for_list_of_available_extensions \
 " SELECT pg_catalog.quote_ident(name) "\
 "   FROM pg_catalog.pg_available_extensions "\
-"  WHERE substring(pg_catalog.quote_ident(name),1,%d)='%s' AND installed IS NULL"
+"  WHERE substring(pg_catalog.quote_ident(name),1,%d)='%s' AND installed_version IS NULL"
 
 /*
  * This is a list of all "things" in Pgsql, which can show up after CREATE or

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201102121
+#define CATALOG_VERSION_NO	201102141
 
 #endif

src/include/catalog/pg_proc.h

@@ -4878,9 +4878,13 @@ DATA(insert OID = 2987 (  btrecordcmp	   PGNSP PGUID 12 1 0 0 f f f t f i 2 0 23
 DESCR("btree less-equal-greater");
 
 /* Extensions */
-DATA(insert OID = 3082 (  pg_available_extensions		PGNSP PGUID 12 10 100 0 f f f t t s 0 0 2249 "" "{19,25,16,25}" "{o,o,o,o}" "{name,version,relocatable,comment}" _null_ pg_available_extensions _null_ _null_ _null_ ));
+DATA(insert OID = 3082 (  pg_available_extensions		PGNSP PGUID 12 10 100 0 f f f t t s 0 0 2249 "" "{19,25,25}" "{o,o,o}" "{name,default_version,comment}" _null_ pg_available_extensions _null_ _null_ _null_ ));
 DESCR("list available extensions");
-DATA(insert OID = 3083 (  pg_extension_config_dump		PGNSP PGUID 12 1 0 0 f f f t f v 2 0 2278 "2205 25" _null_ _null_ _null_ _null_ pg_extension_config_dump _null_ _null_ _null_ ));
+DATA(insert OID = 3083 (  pg_available_extension_versions	PGNSP PGUID 12 10 100 0 f f f t t s 0 0 2249 "" "{19,25,16,19,1003,25}" "{o,o,o,o,o,o}" "{name,version,relocatable,schema,requires,comment}" _null_ pg_available_extension_versions _null_ _null_ _null_ ));
+DESCR("list available extension versions");
+DATA(insert OID = 3084 (  pg_extension_update_paths		PGNSP PGUID 12 10 100 0 f f f t t s 1 0 2249 "19" "{19,25,25,25}" "{i,o,o,o}" "{name,source,target,path}" _null_ pg_extension_update_paths _null_ _null_ _null_ ));
+DESCR("list an extension's version update paths");
+DATA(insert OID = 3086 (  pg_extension_config_dump		PGNSP PGUID 12 1 0 0 f f f t f v 2 0 2278 "2205 25" _null_ _null_ _null_ _null_ pg_extension_config_dump _null_ _null_ _null_ ));
 DESCR("flag an extension's table contents to be emitted by pg_dump");
 
 /* SQL-spec window functions */

src/include/utils/builtins.h

@@ -1067,6 +1067,8 @@ extern Datum unique_key_recheck(PG_FUNCTION_ARGS);
 
 /* commands/extension.c */
 extern Datum pg_available_extensions(PG_FUNCTION_ARGS);
+extern Datum pg_available_extension_versions(PG_FUNCTION_ARGS);
+extern Datum pg_extension_update_paths(PG_FUNCTION_ARGS);
 extern Datum pg_extension_config_dump(PG_FUNCTION_ARGS);
 
 /* commands/prepare.c */

src/test/regress/expected/rules.out

@@ -1277,9 +1277,10 @@ drop table cchild;
 --
 SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schema' ORDER BY viewname;
             viewname             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              definition                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+---------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  iexit                           | SELECT ih.name, ih.thepath, interpt_pp(ih.thepath, r.thepath) AS exit FROM ihighway ih, ramp r WHERE (ih.thepath ## r.thepath);
- pg_available_extensions     | SELECT e.name, e.version, x.extversion AS installed, n.nspname AS schema, e.relocatable, e.comment FROM ((pg_available_extensions() e(name, version, relocatable, comment) LEFT JOIN pg_extension x ON ((e.name = x.extname))) LEFT JOIN pg_namespace n ON ((n.oid = x.extnamespace)));
+ pg_available_extension_versions | SELECT e.name, e.version, (x.extname IS NOT NULL) AS installed, e.relocatable, e.schema, e.requires, e.comment FROM (pg_available_extension_versions() e(name, version, relocatable, schema, requires, comment) LEFT JOIN pg_extension x ON (((e.name = x.extname) AND (e.version = x.extversion))));
+ pg_available_extensions         | SELECT e.name, e.default_version, x.extversion AS installed_version, e.comment FROM (pg_available_extensions() e(name, default_version, comment) LEFT JOIN pg_extension x ON ((e.name = x.extname)));
  pg_cursors                      | SELECT c.name, c.statement, c.is_holdable, c.is_binary, c.is_scrollable, c.creation_time FROM pg_cursor() c(name, statement, is_holdable, is_binary, is_scrollable, creation_time);
  pg_group                        | SELECT pg_authid.rolname AS groname, pg_authid.oid AS grosysid, ARRAY(SELECT pg_auth_members.member FROM pg_auth_members WHERE (pg_auth_members.roleid = pg_authid.oid)) AS grolist FROM pg_authid WHERE (NOT pg_authid.rolcanlogin);
  pg_indexes                      | SELECT n.nspname AS schemaname, c.relname AS tablename, i.relname AS indexname, t.spcname AS tablespace, pg_get_indexdef(i.oid) AS indexdef FROM ((((pg_index x JOIN pg_class c ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = i.reltablespace))) WHERE ((c.relkind = 'r'::"char") AND (i.relkind = 'i'::"char"));
@@ -1337,7 +1338,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  shoelace_obsolete               | SELECT shoelace.sl_name, shoelace.sl_avail, shoelace.sl_color, shoelace.sl_len, shoelace.sl_unit, shoelace.sl_len_cm FROM shoelace WHERE (NOT (EXISTS (SELECT shoe.shoename FROM shoe WHERE (shoe.slcolor = shoelace.sl_color))));
  street                          | SELECT r.name, r.thepath, c.cname FROM ONLY road r, real_city c WHERE (c.outline ## r.thepath);
  toyemp                          | SELECT emp.name, emp.age, emp.location, (12 * emp.salary) AS annualsal FROM emp;
-(59 rows)
+(60 rows)
 
 SELECT tablename, rulename, definition FROM pg_rules
 	ORDER BY tablename, rulename;