Maybe we should fire a jira if it is a bug.
Best, Danny Chan 在 2019年3月26日 +0800 PM8:33，Hongze Zhang <[email protected]>，写道： > Ops, correct a typo: > > "... after uncommenting a line ..." -> "... after commenting a line > ...". > > Best, > Hongze > > ------ Original Message ------ > From: "Hongze Zhang" <[email protected]> > To: [email protected] > Sent: 2019/3/26 19:28:08 > Subject: Re: Calcite doesn't work with LOOKAHEAD(3) > > > Firstly, thank you very much for sharing the case, Rui! > > > > I have run a test with the SQL you provided and also run into the same > > exception (under a global LOOKAHEAD 3). After debugging the generated > > parser code, I think the problem is probably in the generated LOOKAHEAD > > method SqlParserImpl#jj_3R_42(): > > > > > > > final private boolean jj_3R_42() { > > > if (!jj_rescan) trace_call("SqlSelect(LOOKING AHEAD...)"); > > > if (jj_scan_token(SELECT)) { if (!jj_rescan) > > > trace_return("SqlSelect(LOOKAHEAD FAILED)"); return true; } > > > if (jj_3R_190()) { if (!jj_rescan) trace_return("SqlSelect(LOOKAHEAD > > > FAILED)"); return true; } > > > { if (!jj_rescan) trace_return("SqlSelect(LOOKAHEAD SUCCEEDED)"); return > > > false; } > > > } > > > > The LOOKAHEAD method checks only a single token <SELECT>. This is > > definitely not enough since we have already set the number to 3. > > > > Unfortunately I didn't find a root cause so far, but after uncommenting a > > line[1] in production "SqlSelect()" then everything goes back to normal. > > I'm inclined to believe JavaCC has some unexpected behavior when dealing > > with LOOKAHEAD on a production with the shape like "SqlSelectKeywords()"[2]. > > > > Please feel free to log a JIRA ticket with which we can track further > > information of the issue. > > > > Best, > > Hongze > > > > > > [1] > > https://github.com/apache/calcite/blob/1b430721c0d9e22b2252ffcd893b42959cb7966c/core/src/main/codegen/templates/Parser.jj#L1030 > > [2] > > https://github.com/apache/calcite/blob/1b430721c0d9e22b2252ffcd893b42959cb7966c/core/src/main/codegen/templates/Parser.jj#L288 > > > > ------ Original Message ------ > > From: "Rui Li" <[email protected]> > > To: [email protected] > > Sent: 2019/3/26 16:53:44 > > Subject: Calcite doesn't work with LOOKAHEAD(3) > > > > > Hi, > > > > > > I'm trying to extend Calcite grammar to support some custom statements. > > > And > > > I need to increase LOOKAHEAD to 3 to resolve some ambiguity. But when I > > > did > > > that, the parser fails to parse queries like: > > > * select t.key from (select key from src) t* > > > > > > With exception: > > > *Caused by: org.apache.calcite.sql.parser.impl.ParseException:* > > > *Encountered "( select key" at line 1, column 19.* > > > *Was expecting one of:* > > > * <IDENTIFIER> ...* > > > * <QUOTED_IDENTIFIER> ...* > > > * <BACK_QUOTED_IDENTIFIER> ...* > > > * <BRACKET_QUOTED_IDENTIFIER> ...* > > > * <UNICODE_QUOTED_IDENTIFIER> ...* > > > * "LATERAL" ...* > > > * "(" "WITH" ...* > > > *...* > > > > > > So I'm wondering whether there's some limitation on the LOOKAHEAD we can > > > use? > > > > > > -- > > > Best regards! > > > Rui Li
