[GitHub] morningman commented on issue #381: Support 'NO_BACKSLASH_ESCAPES' sql_mode

[GitBox <gi...@apache.org>]

morningman commented on issue #381: Support 'NO_BACKSLASH_ESCAPES' sql_mode
URL: https://github.com/apache/incubator-doris/issues/381#issuecomment-444464498
 
 
   The 'NO_BACKSLASH_ESCAPES' sql_mode we supported before does not have same meaning as MySQL's sql_mode with same name.
   
   In MySQL, 'NO_BACKSLASH_ESCAPES' means to ignore the backslash at the very beginning of lexical parsing phase. But what we implemented in Doris, is to ignore backslash just in accepted quoted string.
   
   In MySQL, if sql_mode is set to 'NO_BACKSLASH_ESCAPES', the following stmt will not be accepted:
   
   `select * from tbl where k1 'ab\'c'`;
   
   But in Doris, this stmt is accepted with sql_mode set to 'NO_BACKSLASH_ESCAPES'.
   Because in Doris, jflex is used as lexical parser, which does not support ignoring backslash when parsing the origin string. So first, jflex will accept the string `'ab\'c'` as `ab'c`. And than it makes a further analysis to this string, determine whether to keep the backslash or not. (`ab'c` or `ab\'c`).

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