Teach psql to display comments on languages and casts.

The output of \dL (list languages) is fairly narrow, so we just always
display the comment.  \dC (list casts) can get fairly wide, so we only
display comments if the new \dC+ option is specified.

Josh Kupershmidt

doc/src/sgml/ref/psql-ref.sgml

@@ -966,7 +966,7 @@ testdb=>
 
 
       <varlistentry>
-        <term><literal>\dC [ <link linkend="APP-PSQL-patterns"><replaceable class="parameter">pattern</replaceable></link> ]</literal></term>
+        <term><literal>\dC[+] [ <link linkend="APP-PSQL-patterns"><replaceable class="parameter">pattern</replaceable></link> ]</literal></term>
         <listitem>
         <para>
         Lists type casts.

src/bin/psql/command.c

@@ -381,7 +381,7 @@ exec_command(const char *cmd,
 				success = listConversions(pattern, show_system);
 				break;
 			case 'C':
-				success = listCasts(pattern);
+				success = listCasts(pattern, show_verbose);
 				break;
 			case 'd':
 				if (strncmp(cmd, "ddp", 3) == 0)

src/bin/psql/describe.c

@@ -2647,8 +2647,10 @@ listLanguages(const char *pattern, bool verbose, bool showSystem)
 						  gettext_noop("Owner"));
 
 	appendPQExpBuffer(&buf,
-					  "       l.lanpltrusted AS \"%s\"",
-					  gettext_noop("Trusted"));
+					  "       l.lanpltrusted AS \"%s\",\n"
+					  "       d.description AS \"%s\"",
+					  gettext_noop("Trusted"),
+					  gettext_noop("Description"));
 
 	if (verbose)
 	{
@@ -2666,13 +2668,18 @@ listLanguages(const char *pattern, bool verbose, bool showSystem)
 	}
 
 	appendPQExpBuffer(&buf,
-					  "\nFROM pg_catalog.pg_language l\n");
+					  "\nFROM pg_catalog.pg_language l\n"
+					  "LEFT JOIN pg_catalog.pg_description d\n"
+					  "  ON d.classoid = l.tableoid AND d.objoid = l.oid\n"
+					  "  AND d.objsubid = 0\n");
 
-	processSQLNamePattern(pset.db, &buf, pattern, false, false,
-						  NULL, "l.lanname", NULL, NULL);
+	if (pattern)
+		processSQLNamePattern(pset.db, &buf, pattern, false, false,
+							  NULL, "l.lanname", NULL, NULL);
 
 	if (!showSystem && !pattern)
-		appendPQExpBuffer(&buf, "WHERE lanplcallfoid != 0\n");
+		appendPQExpBuffer(&buf, "WHERE l.lanplcallfoid != 0\n");
+
 
 	appendPQExpBuffer(&buf, "ORDER BY 1;");
 
@@ -2820,7 +2827,7 @@ listConversions(const char *pattern, bool showSystem)
  * Describes casts.
  */
 bool
-listCasts(const char *pattern)
+listCasts(const char *pattern, bool verbose)
 {
 	PQExpBufferData buf;
 	PGresult   *res;
@@ -2844,7 +2851,21 @@ listCasts(const char *pattern)
 					  "       CASE WHEN c.castcontext = 'e' THEN '%s'\n"
 					  "            WHEN c.castcontext = 'a' THEN '%s'\n"
 					  "            ELSE '%s'\n"
-					  "       END as \"%s\"\n"
+					  "       END as \"%s\"",
+					  gettext_noop("Source type"),
+					  gettext_noop("Target type"),
+					  gettext_noop("Function"),
+					  gettext_noop("no"),
+					  gettext_noop("in assignment"),
+					  gettext_noop("yes"),
+					  gettext_noop("Implicit?"));
+
+	if (verbose)
+		appendPQExpBuffer(&buf,
+						  ",\n       d.description AS \"%s\"\n",
+						  gettext_noop("Description"));
+
+	appendPQExpBuffer(&buf,
 				 "FROM pg_catalog.pg_cast c LEFT JOIN pg_catalog.pg_proc p\n"
 					  "     ON c.castfunc = p.oid\n"
 					  "     LEFT JOIN pg_catalog.pg_type ts\n"
@@ -2854,13 +2875,15 @@ listCasts(const char *pattern)
 					  "     LEFT JOIN pg_catalog.pg_type tt\n"
 					  "     ON c.casttarget = tt.oid\n"
 					  "     LEFT JOIN pg_catalog.pg_namespace nt\n"
-					  "     ON nt.oid = tt.typnamespace\n"
-					  "WHERE (true",
-					  gettext_noop("Source type"),
-					  gettext_noop("Target type"),
-					  gettext_noop("Function"),
-	  gettext_noop("no"), gettext_noop("in assignment"), gettext_noop("yes"),
-					  gettext_noop("Implicit?"));
+					  "     ON nt.oid = tt.typnamespace\n");
+
+	if (verbose)
+		appendPQExpBuffer(&buf,
+						  "     LEFT JOIN pg_catalog.pg_description d\n"
+						  "     ON d.classoid = c.tableoid AND d.objoid = "
+						  "c.oid AND d.objsubid = 0\n");
+
+	appendPQExpBuffer(&buf, "WHERE ( (true");
 
 	/*
 	 * Match name pattern against either internal or external name of either
@@ -2878,7 +2901,7 @@ listCasts(const char *pattern)
 						  "pg_catalog.format_type(tt.oid, NULL)",
 						  "pg_catalog.pg_type_is_visible(tt.oid)");
 
-	appendPQExpBuffer(&buf, ")\nORDER BY 1, 2;");
+	appendPQExpBuffer(&buf, ") )\nORDER BY 1, 2;");
 
 	res = PSQLexec(buf.data, false);
 	termPQExpBuffer(&buf);

src/bin/psql/describe.h

@@ -67,7 +67,7 @@ extern bool listDomains(const char *pattern, bool showSystem);
 extern bool listConversions(const char *pattern, bool showSystem);
 
 /* \dC */
-extern bool listCasts(const char *pattern);
+extern bool listCasts(const char *pattern, bool verbose);
 
 /* \dO */
 extern bool listCollations(const char *pattern, bool verbose, bool showSystem);

src/bin/psql/help.c

@@ -196,7 +196,7 @@ slashUsage(unsigned short int pager)
 	fprintf(output, _("  \\da[S]  [PATTERN]      list aggregates\n"));
 	fprintf(output, _("  \\db[+]  [PATTERN]      list tablespaces\n"));
 	fprintf(output, _("  \\dc[S]  [PATTERN]      list conversions\n"));
-	fprintf(output, _("  \\dC     [PATTERN]      list casts\n"));
+	fprintf(output, _("  \\dC[+]  [PATTERN]      list casts\n"));
 	fprintf(output, _("  \\dd[S]  [PATTERN]      show comments on objects\n"));
 	fprintf(output, _("  \\ddp    [PATTERN]      list default privileges\n"));
 	fprintf(output, _("  \\dD[S]  [PATTERN]      list domains\n"));