Experiment on parsing backslash escapes in a more convenient way #10922

src/IO/ReadHelpers.cpp

@@ -283,23 +283,40 @@ static void parseComplexEscapeSequence(Vector & s, ReadBuffer & buf)
     if (buf.eof())
         throw Exception("Cannot parse escape sequence", ErrorCodes::CANNOT_PARSE_ESCAPE_SEQUENCE);
 
-    if (*buf.position() == 'x')
+    char char_after_backslash = *buf.position();
+
+    if (char_after_backslash == 'x')
     {
         ++buf.position();
         /// escape sequence of the form \xAA
         char hex_code[2];
         readPODBinary(hex_code, buf);
         s.push_back(unhex2(hex_code));
     }
-    else if (*buf.position() == 'N')
+    else if (char_after_backslash == 'N')
     {
         /// Support for NULLs: \N sequence must be parsed as empty string.
         ++buf.position();
     }
     else
     {
         /// The usual escape sequence of a single character.
-        s.push_back(parseEscapeSequence(*buf.position()));
+        char decoded_char = parseEscapeSequence(char_after_backslash);
+
+        /// For convenience using LIKE and regular expressions,
+        /// we leave backslash when user write something like 'Hello 100\%':
+        /// it is parsed like Hello 100\% instead of Hello 100%
+        if (decoded_char != '\\'
+            && decoded_char != '\''
+            && decoded_char != '"'
+            && decoded_char != '`'  /// MySQL style identifiers
+            && decoded_char != '/'  /// JavaScript in HTML
+            && !isControlASCII(decoded_char))
+        {
+            s.push_back('\\');
+        }
+
+        s.push_back(decoded_char);
         ++buf.position();
     }
 }

src/IO/tests/CMakeLists.txt

@@ -37,9 +37,6 @@ target_link_libraries (parse_int_perf2 PRIVATE clickhouse_common_io)
 add_executable (read_write_int read_write_int.cpp)
 target_link_libraries (read_write_int PRIVATE clickhouse_common_io)
 
-add_executable (mempbrk mempbrk.cpp)
-target_link_libraries (mempbrk PRIVATE clickhouse_common_io)
-
 add_executable (o_direct_and_dirty_pages o_direct_and_dirty_pages.cpp)
 target_link_libraries (o_direct_and_dirty_pages PRIVATE clickhouse_common_io)
 

tests/queries/0_stateless/00342_escape_sequences.reference

@@ -1 +1 @@
-07080C0A0D090B5C27223FAA
+07080C0A0D090B5C27225C3FAA

tests/queries/0_stateless/00926_multimatch.sql

@@ -89,4 +89,4 @@ SELECT [1, 2, 3, 11] = arraySort(multiMatchAllIndices('фабрикант', ['',
 SELECT [1] = multiMatchAllIndices(materialize('/odezhda-dlya-bega/'), ['/odezhda-dlya-bega/', 'kurtki-i-vetrovki-dlya-bega', 'futbolki-i-mayki-dlya-bega']);
 SELECT [] = multiMatchAllIndices(materialize('aaaa'), ['.*aa.*aaa.*', 'aaaaaa{2}', '\(aa\){3}']);
 SELECT 'All tests above must return 1, all tests below return something.';
-SELECT arraySort(multiMatchAllIndices(arrayJoin(['aaaa', 'aaaaaa', 'bbbb', 'aaaaaaaaaaaaaa']), ['.*aa.*aaa.*', 'aaaaaa{2}', '\(aa\){3}']));
+SELECT arraySort(multiMatchAllIndices(arrayJoin(['aaaa', 'aaaaaa', 'bbbb', 'aaaaaaaaaaaaaa']), ['.*aa.*aaa.*', 'aaaaaa{2}', '(aa){3}']));

tests/queries/0_stateless/01075_allowed_client_hosts.reference

@@ -8,10 +8,10 @@ CREATE USER test_user_01075 HOST LOCAL, IP \'2001:db8:11a3:9d7:1f34:8a2e:7a0:765
 CREATE USER test_user_01075 HOST LOCAL
 CREATE USER test_user_01075 HOST NONE
 CREATE USER test_user_01075 HOST LIKE \'@.somesite.com\'
-CREATE USER test_user_01075 HOST REGEXP \'.*.anothersite.com\'
-CREATE USER test_user_01075 HOST REGEXP \'.*.anothersite.com\', \'.*.anothersite.org\'
-CREATE USER test_user_01075 HOST REGEXP \'.*.anothersite2.com\', \'.*.anothersite2.org\'
-CREATE USER test_user_01075 HOST REGEXP \'.*.anothersite3.com\', \'.*.anothersite3.org\'
+CREATE USER test_user_01075 HOST REGEXP \'.*\\\\.anothersite\\\\.com\'
+CREATE USER test_user_01075 HOST REGEXP \'.*\\\\.anothersite\\\\.com\', \'.*\\\\.anothersite\\\\.org\'
+CREATE USER test_user_01075 HOST REGEXP \'.*\\\\.anothersite2\\\\.com\', \'.*\\\\.anothersite2\\\\.org\'
+CREATE USER test_user_01075 HOST REGEXP \'.*\\\\.anothersite3\\\\.com\', \'.*\\\\.anothersite3\\\\.org\'
 CREATE USER `test_user_01075_x@localhost` HOST LOCAL
 CREATE USER test_user_01075_x
 CREATE USER `test_user_01075_x@192.168.23.15` HOST LIKE \'192.168.23.15\'

tests/queries/0_stateless/01284_escape_sequences_php_mysql_style.reference

@@ -0,0 +1,3 @@
+a\\_\\c\\l\\i\\c\\k\\h\\o\\u\\s	a\\_\\c\\l\\i\\c\\k\\h\\o\\u\\s\\e
+1	0	1	1
+1	1	0	0	0

tests/queries/0_stateless/01284_escape_sequences_php_mysql_style.sql

@@ -0,0 +1,6 @@
+SELECT 'a\_\c\l\i\c\k\h\o\u\s\e', 'a\\_\\c\\l\\i\\c\\k\\h\\o\\u\\s\\e';
+select 'aXb' like 'a_b', 'aXb' like 'a\_b', 'a_b' like 'a\_b', 'a_b' like 'a\\_b';
+SELECT match('Hello', '\w+'), match('Hello', '\\w+'), match('Hello', '\\\w+'), match('Hello', '\w\+'), match('Hello', 'w+');
+
+SELECT match('Hello', '\He\l\l\o'); -- { serverError 427 }
+SELECT match('Hello', '\H\e\l\l\o'); -- { serverError 427 }