[GitHub] [incubator-iotdb] Ring-k commented on issue #440: reconstruct antlrv3 grammar to improve performance

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Ring-k commented on issue #440: reconstruct antlrv3 grammar to improve performance
URL: https://github.com/apache/incubator-iotdb/pull/440#issuecomment-541295084
 
 
   The core idea of this reconstruction is
   1. The statement is now grouped as ddlStatement, dmlStatement, and administrationStatement, which is more consistent with the conventional sql design.
   2. I reorganize the format of constant. In previous version, we have negetive integer, positive integer, usigned integer, etc. To aviod problems of longest match, we need to use "=>" operator. This operator is widely used in previous version. I simplified the grammer definition by just defining the integer and real numbers, regardless of the sign. No "=>" operator anymore. Althought, some acceptable constraints are introduced, like "+" is not allowed to identify a positive value. I think because of less checkings during parsing, the performance is improved, especially in parsing full-digit paths.

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