From d54ceb9e176152f930e60709e07c636e8e5414f5 Mon Sep 17 00:00:00 2001
From: Alexander Korotkov <akorotkov@postgresql.org>
Date: Sun, 11 Aug 2019 22:54:53 +0300
Subject: Adjust string comparison in jsonpath

We have implemented jsonpath string comparison using default database locale.
However, standard requires us to compare Unicode codepoints.  This commit
implements that, but for performance reasons we still use per-byte comparison
for "==" operator.  Thus, for consistency other comparison operators do per-byte
comparison if Unicode codepoints appear to be equal.

In some edge cases, when same Unicode codepoints have different binary
representations in database encoding, we diverge standard to achieve better
performance of "==" operator.  In future to implement strict standard
conformance, we can do normalization of input JSON strings.

Original patch was written by Nikita Glukhov, rewritten by me.

Reported-by: Markus Winand
Discussion: https://postgr.es/m/8B7FA3B4-328D-43D7-95A8-37B8891B8C78%40winand.at
Author: Nikita Glukhov, Alexander Korotkov
Backpatch-through: 12
---
 src/test/regress/sql/jsonb_jsonpath.sql | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'src/test/regress/sql/jsonb_jsonpath.sql')

diff --git a/src/test/regress/sql/jsonb_jsonpath.sql b/src/test/regress/sql/jsonb_jsonpath.sql
index 733fbd4e0d0..e7629fb7f9d 100644
--- a/src/test/regress/sql/jsonb_jsonpath.sql
+++ b/src/test/regress/sql/jsonb_jsonpath.sql
@@ -387,3 +387,19 @@ SELECT jsonb_path_match('[true, true]', '$[*]', silent => false);
 SELECT jsonb '[{"a": 1}, {"a": 2}]' @@ '$[*].a > 1';
 SELECT jsonb '[{"a": 1}, {"a": 2}]' @@ '$[*].a > 2';
 SELECT jsonb_path_match('[{"a": 1}, {"a": 2}]', '$[*].a > 1');
+
+-- test string comparison (Unicode codepoint collation)
+WITH str(j, num) AS
+(
+	SELECT jsonb_build_object('s', s), num
+	FROM unnest('{"", "a", "ab", "abc", "abcd", "b", "A", "AB", "ABC", "ABc", "ABcD", "B"}'::text[]) WITH ORDINALITY AS a(s, num)
+)
+SELECT
+	s1.j, s2.j,
+	jsonb_path_query_first(s1.j, '$.s < $s', vars => s2.j) lt,
+	jsonb_path_query_first(s1.j, '$.s <= $s', vars => s2.j) le,
+	jsonb_path_query_first(s1.j, '$.s == $s', vars => s2.j) eq,
+	jsonb_path_query_first(s1.j, '$.s >= $s', vars => s2.j) ge,
+	jsonb_path_query_first(s1.j, '$.s > $s', vars => s2.j) gt
+FROM str s1, str s2
+ORDER BY s1.num, s2.num;
-- 
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