Introduction to gbase8s SQL Engine framework

GBase8s Of SQL The engine consists of the following parts ：

         Syntax file generator 、 Syntax parser 、 Optimizer 、 actuator

Syntax file generator ：

         Pass the syntax file through external tools yacc, According to the version 、 Platform and other information to generate syntax parsing files

Syntax parser ：

         Enter the user into sql Query statement , for example “select name from company_table where id = 28;” The syntax and semantic analysis is carried out through the syntax analysis file generated by the syntax file , And finally generate the syntax query tree .

Optimizer ：

Transform syntax query tree into logical relation query tree ;

Pair projection 、 Choose and other operations to optimize sentence patterns ; Optimize the predicate of conditional expression 、 Conditional simplification ;

The connection statement is externally connected 、 Nested join optimization ;

Sub query optimization 、 View reconstruction 、 Semantic optimization and other technologies to optimize the query .

Find the path that costs the least , The query execution plan is generated accordingly .

1. actuator ：

SQL Query execution module , Execute the plan according to the optimal query , Get the query results , And return to the user .