[db_metadata] Replacing boost ptree by rapidjson

Summary:
Rapidjson is more efficient in JSON parsing. This code was left out
while migrating most of trx_meta_data code.

Test Plan: mtr

Reviewers: yashb, arahut

Reviewed By: yashb

Subscribers: butterflybot, ritwikyadav, vinaybhat, webscalesql-eng@fb.com

Differential Revision: https://phabricator.intern.facebook.com/D15967068

Tasks: T35788404

Signature: 15967068:1562090840:7c08912bf5b6fcb18515c53c7e9d692e05b0dd9e

sql/sql_class.cc

@@ -69,6 +69,10 @@
 #include <boost/lexical_cast.hpp>
 #include <boost/property_tree/ptree.hpp>
 #include <boost/property_tree/json_parser.hpp>
+#ifdef HAVE_RAPIDJSON
+#include "rapidjson/document.h"
+#include "rapidjson/writer.h"
+#endif
 #include <sstream>
 
 #ifdef TARGET_OS_LINUX
@@ -5788,10 +5792,22 @@ int THD::parse_query_info_attr()
 static std::string get_shard_id(const std::string& db_metadata)
 {
   try {
+#ifdef HAVE_RAPIDJSON
+    rapidjson::Document db_metadata_root;
+    if (db_metadata_root.Parse(db_metadata.c_str()).HasParseError()) {
+      return {};
+    }
+    const auto iter= db_metadata_root.FindMember("shard");
+    std::string shard_id;
+    if (iter == db_metadata_root.MemberEnd()) {
+      shard_id= iter->value.GetString();
+    }
+#else
     boost::property_tree::ptree db_metadata_root;
     std::istringstream is(db_metadata);
     boost::property_tree::read_json(is, db_metadata_root);
     std::string shard_id = db_metadata_root.get<std::string>("shard");
+#endif
     return shard_id;
   }
   catch (std::exception)

sql/sql_yacc.yy

@@ -66,8 +66,13 @@ Note: YYTHD is passed as an argument to yyparse(), and subsequently to yylex().
 #include "opt_explain_json.h"
 #include "lex_token.h"
 #include <sstream>
+#ifdef HAVE_RAPIDJSON
+#include "rapidjson/document.h"
+#include "rapidjson/writer.h"
+#else
 #include <boost/property_tree/ptree.hpp>
 #include <boost/property_tree/json_parser.hpp>
+#endif
 
 /* this is to get the bison compilation windows warnings out */
 #ifdef _MSC_VER
@@ -6579,6 +6584,14 @@ db_metadata_str:
             /* Verify that a valid JSON is provided */
             if ($3.length > 0)
             {
+              #ifdef HAVE_RAPIDJSON
+              rapidjson::Document db_metadata_root;
+              if (db_metadata_root.Parse($3.str).HasParseError())
+              {
+                my_error(ER_DB_METADATA_INVALID_JSON, MYF(0), $3.str);
+                MYSQL_YYABORT;
+              }
+              #else
               boost::property_tree::ptree db_metadata_root;
               std::istringstream is($3.str);
               try
@@ -6591,6 +6604,7 @@ db_metadata_str:
                 my_error(ER_DB_METADATA_INVALID_JSON, MYF(0), $3.str);
                 MYSQL_YYABORT;
               }
+              #endif
             }
             Lex->create_info.db_metadata= String($3.str, $3.length,
               &my_charset_bin);