Zhen Li created SPARK-38378:
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Summary: ANTLR grammar definition in separate Parser and Lexer
files
Key: SPARK-38378
URL: https://issues.apache.org/jira/browse/SPARK-38378
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 3.3.0, 3.2.2
Reporter: Zhen Li
Suggesting to separate the ANTLR grammar defined in `SqlBase.g4` into separate
parser `SqlBaseParser.g4` and lexer `SqlBaseLexer.g4`.
Benefits:
*Gain more flexibility when implementing new SQL features*
The current ANTLR grammar definition is given as a mixed grammar in the
`SqlBase.g4` file.
By separating the lexer and parser, we will be able to use the full power of
ANTLR parser and lexer grammars. e.g. lexer mode. This will give us more
flexibility when implementing new SQL features.
*The code is more clean.*
Having parser and lexer in different files also keeps the code more explicit
about which is the parser and which is the lexer.
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