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

diff --git a/src/backend/utils/adt/jsonpath_exec.c b/src/backend/utils/adt/jsonpath_exec.c
index 293d6da027cf0c1b656e3a0326219980d45cbcbf..4a0de4fe95a616ee6f61d0719f539f2f96ff9d09 100644 (file)
--- a/src/backend/utils/adt/jsonpath_exec.c
+++ b/src/backend/utils/adt/jsonpath_exec.c
@@ -1980,6 +1980,73 @@ executeComparison(JsonPathItem *cmp, JsonbValue *lv, JsonbValue *rv, void *p)
        return compareItems(cmp->type, lv, rv);
 }
 
+/*
+ * Perform per-byte comparison of two strings.
+ */
+static int
+binaryCompareStrings(const char *s1, int len1,
+                                        const char *s2, int len2)
+{
+       int                     cmp;
+
+       cmp = memcmp(s1, s2, Min(len1, len2));
+
+       if (cmp != 0)
+               return cmp;
+
+       if (len1 == len2)
+               return 0;
+
+       return len1 < len2 ? -1 : 1;
+}
+
+/*
+ * Compare two strings in the current server encoding using Unicode codepoint
+ * collation.
+ */
+static int
+compareStrings(const char *mbstr1, int mblen1,
+                          const char *mbstr2, int mblen2)
+{
+       if (GetDatabaseEncoding() == PG_SQL_ASCII ||
+               GetDatabaseEncoding() == PG_UTF8)
+       {
+               /*
+                * It's known property of UTF-8 strings that their per-byte comparison
+                * result matches codepoints comparison result.  ASCII can be
+                * considered as special case of UTF-8.
+                */
+               return binaryCompareStrings(mbstr1, mblen1, mbstr2, mblen2);
+       }
+       else
+       {
+               /* We have to convert other encodings to UTF-8 first, then compare. */
+               char       *utf8str1 = pg_server_to_any(mbstr1, mblen1, PG_UTF8),
+                                  *utf8str2 = pg_server_to_any(mbstr2, mblen2, PG_UTF8);
+               int                     cmp;
+
+               cmp = binaryCompareStrings(utf8str1, strlen(utf8str1),
+                                                                  utf8str2, strlen(utf8str2));
+
+               pfree(utf8str1);
+               pfree(utf8str2);
+
+               /*
+                * When all Unicode codepoints are equal, return result of binary
+                * comparison.  In some edge cases, same characters may have different
+                * representations in encoding.  Then our behavior could diverge from
+                * standard.  However, that allow us to do simple binary comparison
+                * for "==" operator, which is performance critical in typical cases.
+                * In future to implement strict standard conformance, we can do
+                * normalization of input JSON strings.
+                */
+               if (cmp == 0)
+                       return binaryCompareStrings(mbstr1, mblen1, mbstr2, mblen2);
+               else
+                       return cmp;
+       }
+}
+
 /*
  * Compare two SQL/JSON items using comparison operation 'op'.
  */
@@ -2022,9 +2089,8 @@ compareItems(int32 op, JsonbValue *jb1, JsonbValue *jb2)
                                                   jb2->val.string.val,
                                                   jb1->val.string.len) ? jpbFalse : jpbTrue;
 
-                       cmp = varstr_cmp(jb1->val.string.val, jb1->val.string.len,
-                                                        jb2->val.string.val, jb2->val.string.len,
-                                                        DEFAULT_COLLATION_OID);
+                       cmp = compareStrings(jb1->val.string.val, jb1->val.string.len,
+                                                                jb2->val.string.val, jb2->val.string.len);
                        break;
 
                case jbvBinary:

diff --git a/src/test/regress/expected/jsonb_jsonpath.out b/src/test/regress/expected/jsonb_jsonpath.out
index 31a871af0289a8891ae6d58fadbeb8f284ad1aa3..0202667a1f732d04a3285f82594c76e08789b428 100644 (file)
--- a/src/test/regress/expected/jsonb_jsonpath.out
+++ b/src/test/regress/expected/jsonb_jsonpath.out
@@ -1833,3 +1833,166 @@ SELECT jsonb_path_match('[{"a": 1}, {"a": 2}]', '$[*].a > 1');
  t
 (1 row)
 
+-- 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;
+       j       |       j       |  lt   |  le   |  eq   |  ge   |  gt   
+---------------+---------------+-------+-------+-------+-------+-------
+ {"s": ""}     | {"s": ""}     | false | true  | true  | true  | false
+ {"s": ""}     | {"s": "a"}    | true  | true  | false | false | false
+ {"s": ""}     | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": ""}     | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": ""}     | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": ""}     | {"s": "b"}    | true  | true  | false | false | false
+ {"s": ""}     | {"s": "A"}    | true  | true  | false | false | false
+ {"s": ""}     | {"s": "AB"}   | true  | true  | false | false | false
+ {"s": ""}     | {"s": "ABC"}  | true  | true  | false | false | false
+ {"s": ""}     | {"s": "ABc"}  | true  | true  | false | false | false
+ {"s": ""}     | {"s": "ABcD"} | true  | true  | false | false | false
+ {"s": ""}     | {"s": "B"}    | true  | true  | false | false | false
+ {"s": "a"}    | {"s": ""}     | false | false | false | true  | true
+ {"s": "a"}    | {"s": "a"}    | false | true  | true  | true  | false
+ {"s": "a"}    | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "a"}    | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "a"}    | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "a"}    | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "a"}    | {"s": "A"}    | false | false | false | true  | true
+ {"s": "a"}    | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "a"}    | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "a"}    | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "a"}    | {"s": "ABcD"} | false | false | false | true  | true
+ {"s": "a"}    | {"s": "B"}    | false | false | false | true  | true
+ {"s": "ab"}   | {"s": ""}     | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "a"}    | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "ab"}   | false | true  | true  | true  | false
+ {"s": "ab"}   | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "ab"}   | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "ab"}   | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "ab"}   | {"s": "A"}    | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "ABcD"} | false | false | false | true  | true
+ {"s": "ab"}   | {"s": "B"}    | false | false | false | true  | true
+ {"s": "abc"}  | {"s": ""}     | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "a"}    | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "ab"}   | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "abc"}  | false | true  | true  | true  | false
+ {"s": "abc"}  | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "abc"}  | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "abc"}  | {"s": "A"}    | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "ABcD"} | false | false | false | true  | true
+ {"s": "abc"}  | {"s": "B"}    | false | false | false | true  | true
+ {"s": "abcd"} | {"s": ""}     | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "a"}    | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "ab"}   | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "abc"}  | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "abcd"} | false | true  | true  | true  | false
+ {"s": "abcd"} | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "abcd"} | {"s": "A"}    | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "ABcD"} | false | false | false | true  | true
+ {"s": "abcd"} | {"s": "B"}    | false | false | false | true  | true
+ {"s": "b"}    | {"s": ""}     | false | false | false | true  | true
+ {"s": "b"}    | {"s": "a"}    | false | false | false | true  | true
+ {"s": "b"}    | {"s": "ab"}   | false | false | false | true  | true
+ {"s": "b"}    | {"s": "abc"}  | false | false | false | true  | true
+ {"s": "b"}    | {"s": "abcd"} | false | false | false | true  | true
+ {"s": "b"}    | {"s": "b"}    | false | true  | true  | true  | false
+ {"s": "b"}    | {"s": "A"}    | false | false | false | true  | true
+ {"s": "b"}    | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "b"}    | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "b"}    | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "b"}    | {"s": "ABcD"} | false | false | false | true  | true
+ {"s": "b"}    | {"s": "B"}    | false | false | false | true  | true
+ {"s": "A"}    | {"s": ""}     | false | false | false | true  | true
+ {"s": "A"}    | {"s": "a"}    | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "A"}    | false | true  | true  | true  | false
+ {"s": "A"}    | {"s": "AB"}   | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "ABC"}  | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "ABc"}  | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "ABcD"} | true  | true  | false | false | false
+ {"s": "A"}    | {"s": "B"}    | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": ""}     | false | false | false | true  | true
+ {"s": "AB"}   | {"s": "a"}    | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "A"}    | false | false | false | true  | true
+ {"s": "AB"}   | {"s": "AB"}   | false | true  | true  | true  | false
+ {"s": "AB"}   | {"s": "ABC"}  | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "ABc"}  | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "ABcD"} | true  | true  | false | false | false
+ {"s": "AB"}   | {"s": "B"}    | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": ""}     | false | false | false | true  | true
+ {"s": "ABC"}  | {"s": "a"}    | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "A"}    | false | false | false | true  | true
+ {"s": "ABC"}  | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "ABC"}  | {"s": "ABC"}  | false | true  | true  | true  | false
+ {"s": "ABC"}  | {"s": "ABc"}  | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "ABcD"} | true  | true  | false | false | false
+ {"s": "ABC"}  | {"s": "B"}    | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": ""}     | false | false | false | true  | true
+ {"s": "ABc"}  | {"s": "a"}    | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": "A"}    | false | false | false | true  | true
+ {"s": "ABc"}  | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "ABc"}  | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "ABc"}  | {"s": "ABc"}  | false | true  | true  | true  | false
+ {"s": "ABc"}  | {"s": "ABcD"} | true  | true  | false | false | false
+ {"s": "ABc"}  | {"s": "B"}    | true  | true  | false | false | false
+ {"s": "ABcD"} | {"s": ""}     | false | false | false | true  | true
+ {"s": "ABcD"} | {"s": "a"}    | true  | true  | false | false | false
+ {"s": "ABcD"} | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "ABcD"} | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "ABcD"} | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "ABcD"} | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "ABcD"} | {"s": "A"}    | false | false | false | true  | true
+ {"s": "ABcD"} | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "ABcD"} | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "ABcD"} | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "ABcD"} | {"s": "ABcD"} | false | true  | true  | true  | false
+ {"s": "ABcD"} | {"s": "B"}    | true  | true  | false | false | false
+ {"s": "B"}    | {"s": ""}     | false | false | false | true  | true
+ {"s": "B"}    | {"s": "a"}    | true  | true  | false | false | false
+ {"s": "B"}    | {"s": "ab"}   | true  | true  | false | false | false
+ {"s": "B"}    | {"s": "abc"}  | true  | true  | false | false | false
+ {"s": "B"}    | {"s": "abcd"} | true  | true  | false | false | false
+ {"s": "B"}    | {"s": "b"}    | true  | true  | false | false | false
+ {"s": "B"}    | {"s": "A"}    | false | false | false | true  | true
+ {"s": "B"}    | {"s": "AB"}   | false | false | false | true  | true
+ {"s": "B"}    | {"s": "ABC"}  | false | false | false | true  | true
+ {"s": "B"}    | {"s": "ABc"}  | false | false | false | true  | true
+ {"s": "B"}    | {"s": "ABcD"} | false | false | false | true  | true
+ {"s": "B"}    | {"s": "B"}    | false | true  | true  | true  | false
+(144 rows)
+

diff --git a/src/test/regress/sql/jsonb_jsonpath.sql b/src/test/regress/sql/jsonb_jsonpath.sql
index 733fbd4e0d032fd7123a86819fd2a8ef69372f14..e7629fb7f9d99632f8147559d1ed9a68ed1ce7ff 100644 (file)
--- 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;