AbstractSqlParser — Base SQL Parsing Infrastructure¶
AbstractSqlParser
is an extension of the ParserInterface abstraction for SQL parsers that delegate parsing to an AstBuilder.
AbstractSqlParser
is the foundation of the SQL Parsing Framework.
AstBuilder¶
astBuilder: AstBuilder
AstBuilder for parsing SQL statements
Implementations¶
-
CatalystSqlParser for parsing canonical textual representation of data types and schema
-
SparkSqlParser that is the default SQL parser in SessionState
Setting Up SqlBaseLexer and SqlBaseParser for Parsing¶
parse[T](
command: String)(
toResult: SqlBaseParser => T): T
parse
sets up ANTLR parsing infrastructure with SqlBaseLexer
and SqlBaseParser
(which are the ANTLR-specific classes of Spark SQL that are auto-generated at build time from the SqlBase.g4 grammar).
Internally, parse
first prints out the following INFO message to the logs:
Parsing command: [command]
Tip
Enable INFO
logging level for the custom AbstractSqlParser
s to see the above and other INFO messages.
parse
then creates and sets up a SqlBaseLexer
and SqlBaseParser
that in turn passes the latter on to the input toResult
function where the parsing finally happens.
parse
uses SLL
prediction mode for parsing first before falling back to LL
mode.
In case of parsing errors, parse
reports a ParseException
.
parse
is used in all the parse
methods.