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https://issues.apache.org/jira/browse/IOTDB-190?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yuyuan KANG closed IOTDB-190.
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Resolution: Fixed
> switch to ANTLR v4
> ------------------
>
> Key: IOTDB-190
> URL: https://issues.apache.org/jira/browse/IOTDB-190
> Project: Apache IoTDB
> Issue Type: Improvement
> Reporter: Yuyuan KANG
> Priority: Major
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Currently, the system uses ANTLR v3 for query parsing. However, ANTLR v4 has
> some advantages over ANTLR v3.
> # ANTLRv4 uses visitor and listener mechanism，which allows the grammer
> definition independent from programming language (e.g. Java). So it is much
> easier to maintain.
> # In Antlr v3, developers explicitly defines the structure of the tree to
> build using operator '->'. However, Antlr v4 hides the tree structure from
> developers, which simplifies grammer definition and increases the code
> readability.
> # ANTLR v3’s LL(* ) parsing strategy is weaker than v4’s ALL(* ), so v3
> sometimes
> relied on backtracking to properly parse input phrases.
> # ANTLR v3 cannot handle left-recursive rules, while ANTLR v4 can now handle
> direct left recursion. Therefore, ANTLR v4 can handle more grammer rules.
> # ANTLR v4 works faster than ANTLR v3.
> So it is necessary to switch to ANTLR v4
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