Lift \u0000 constraint in JSON parsing for backward compatibility

Summary:
This is to lift a unicode constraint to allow \u0000 (null) in the JSON string,
for backward data compatibility.

Test Plan: Jenkins

Reviewers: pengt

Reviewed By: pengt

Subscribers: webscalesql-eng

Differential Revision: https://reviews.facebook.net/D54543

fbson/FbsonJsonParser.h

@@ -503,7 +503,7 @@ class FbsonJsonParserT {
           For DC00 to DFFF, it should be low surrogates for UTF16.
           So if it display in the high bits, it's invalid.
         */
-        if ((uc >= 0xDC00 && uc <= 0xDFFF) || uc==0){
+        if (uc >= 0xDC00 && uc <= 0xDFFF){
           return false;
         }
 

mysql-test/suite/json/r/type_document_innodb.result

@@ -214,6 +214,8 @@ insert into t4 values(3, "{\"\\b\\f\\n\\r\\t\":\"123\\t\\r\\n\\f\\bABC\"}", "esc
 insert into t4 values(4, "{\"Status\":\"\\u675f\\u5e26\\u7ed3\\u53d1\\u523b\\u5f55\\u673a\\u5076\\u5c14\\u4e94\\u798f\\u805a\\u54e6\"}", "escape of Unicode");
 insert into t4 values(5, "{\"\\u0009\":\"\\u000d\\u000a\"}", "escape of Unicode for control char");
 insert into t4 values(6, "{\"Control\":\"\\u0002\"}", "escape of Unicode for control char");
+insert into t4 values(7, "{\"NULL\":\"\\u0000\"}", "Unicode for NULL");
+insert into t4 values(8, '{"NULL":"\\u0000"}', "Unicode for NULL");
 select * from t4;
 i	a	s
 1	{"Name":"Json\tXia"}	escape in value
@@ -222,6 +224,8 @@ i	a	s
 4	{"Status":"束带结发刻录机偶尔五福聚哦"}	escape of Unicode
 5	{"\t":"\r\n"}	escape of Unicode for control char
 6	{"Control":"\u0002"}	escape of Unicode for control char
+7	{"NULL":""}	Unicode for NULL
+8	{"NULL":""}	Unicode for NULL
 create table t5 (i int(8), a document, s text(255)) engine = innodb;
 insert into t5 values(1, "{\"BAD\":\"123\\u0xDFFE\"}", "Bad Unicode");
 ERROR HY000: Invalid document value: '{"BAD":"123\u0xDFFE"}', pos 14, error 'Invalid string value'

mysql-test/suite/json/t/type_document_innodb.test

@@ -211,6 +211,8 @@ insert into t4 values(3, "{\"\\b\\f\\n\\r\\t\":\"123\\t\\r\\n\\f\\bABC\"}", "esc
 insert into t4 values(4, "{\"Status\":\"\\u675f\\u5e26\\u7ed3\\u53d1\\u523b\\u5f55\\u673a\\u5076\\u5c14\\u4e94\\u798f\\u805a\\u54e6\"}", "escape of Unicode");
 insert into t4 values(5, "{\"\\u0009\":\"\\u000d\\u000a\"}", "escape of Unicode for control char");
 insert into t4 values(6, "{\"Control\":\"\\u0002\"}", "escape of Unicode for control char");
+insert into t4 values(7, "{\"NULL\":\"\\u0000\"}", "Unicode for NULL");
+insert into t4 values(8, '{"NULL":"\\u0000"}', "Unicode for NULL");
 select * from t4;
 
 # Test FBSon with wrong escape