From 7fa3db367986160dee2b2b0bbfb61e1a51d486fd Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 20 Mar 2022 16:06:41 -0400
Subject: [PATCH] psql: handle tab completion of timezone names after "SET
 TIMEZONE TO".
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Dagfinn Ilmari Mannsåker and Tom Lane

Discussion: https://postgr.es/m/87k0curq0w.fsf@wibble.ilmari.org
---
 src/bin/psql/t/010_tab_completion.pl | 13 +++++++++++
 src/bin/psql/tab-complete.c          | 35 ++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/src/bin/psql/t/010_tab_completion.pl b/src/bin/psql/t/010_tab_completion.pl
index a54910680e..2711935a2c 100644
--- a/src/bin/psql/t/010_tab_completion.pl
+++ b/src/bin/psql/t/010_tab_completion.pl
@@ -338,6 +338,19 @@ check_completion(
 
 clear_line();
 
+# check timezone name completion
+check_completion(
+	"SET timezone TO am\t",
+	qr|'America/|,
+	"offer partial timezone name");
+
+check_completion(
+	"new_\t",
+	qr|New_York|,
+	"complete partial timezone name");
+
+clear_line();
+
 # check completion of a keyword offered in addition to object names;
 # such a keyword should obey COMP_KEYWORD_CASE
 foreach (
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 7b331a38ae..183abcc275 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -402,6 +402,24 @@ do { \
 	matches = rl_completion_matches(text, complete_from_schema_query); \
 } while (0)
 
+/*
+ * Timezone completion is mostly like enum label completion, but we work
+ * a little harder since this is a more common use-case.
+ */
+#define COMPLETE_WITH_TIMEZONE_NAME() \
+do { \
+	static const char *const list[] = { "DEFAULT", NULL }; \
+	if (text[0] == '\'') \
+		completion_charp = Query_for_list_of_timezone_names_quoted_in; \
+	else if (start == 0 || rl_line_buffer[start - 1] != '\'') \
+		completion_charp = Query_for_list_of_timezone_names_quoted_out; \
+	else \
+		completion_charp = Query_for_list_of_timezone_names_unquoted; \
+	completion_charpp = list;							  \
+	completion_verbatim = true; \
+	matches = rl_completion_matches(text, complete_from_query); \
+} while (0)
+
 #define COMPLETE_WITH_FUNCTION_ARG(function) \
 do { \
 	set_completion_reference(function); \
@@ -1105,6 +1123,21 @@ static const SchemaQuery Query_for_trigger_of_table = {
 "   FROM pg_catalog.pg_cursors "\
 "  WHERE name LIKE '%s'"
 
+#define Query_for_list_of_timezone_names_unquoted \
+" SELECT name "\
+"   FROM pg_catalog.pg_timezone_names() "\
+"  WHERE pg_catalog.lower(name) LIKE pg_catalog.lower('%s')"
+
+#define Query_for_list_of_timezone_names_quoted_out \
+"SELECT pg_catalog.quote_literal(name) AS name "\
+"  FROM pg_catalog.pg_timezone_names() "\
+" WHERE pg_catalog.lower(name) LIKE pg_catalog.lower('%s')"
+
+#define Query_for_list_of_timezone_names_quoted_in \
+"SELECT pg_catalog.quote_literal(name) AS name "\
+"  FROM pg_catalog.pg_timezone_names() "\
+" WHERE pg_catalog.quote_literal(pg_catalog.lower(name)) LIKE pg_catalog.lower('%s')"
+
 /*
  * These object types were introduced later than our support cutoff of
  * server version 9.2.  We use the VersionedQuery infrastructure so that
@@ -4176,6 +4209,8 @@ psql_completion(const char *text, int start, int end)
 									 " AND nspname NOT LIKE E'pg\\\\_temp%%'",
 									 "DEFAULT");
 		}
+		else if (TailMatches("TimeZone", "TO|="))
+			COMPLETE_WITH_TIMEZONE_NAME();
 		else
 		{
 			/* generic, type based, GUC support */