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Posted to commits@calcite.apache.org by GitBox <gi...@apache.org> on 2019/03/08 04:33:16 UTC
[GitHub] [calcite] zinking commented on a change in pull request #1041:
[CALCITE-2847] Optimize global LOOKAHEAD for SQL parsers
zinking commented on a change in pull request #1041: [CALCITE-2847] Optimize global LOOKAHEAD for SQL parsers
URL: https://github.com/apache/calcite/pull/1041#discussion_r263662652
##########
File path: core/src/main/codegen/templates/Parser.jj
##########
@@ -1698,94 +1700,97 @@ SqlNode FromClause() :
{
e = TableRef()
(
- // Decide whether to read a JOIN clause or a comma, or to quit having
- // seen a single entry FROM clause like 'FROM emps'. See comments
- // elsewhere regarding <COMMA> lookahead.
LOOKAHEAD(2)
- natural = Natural()
- joinType = JoinType()
- e2 = TableRef()
(
- <ON> {
- joinConditionType = JoinConditionType.ON.symbol(getPos());
- }
- condition = Expression(ExprContext.ACCEPT_SUB_QUERY) {
+ // Decide whether to read a JOIN clause or a comma, or to quit having
+ // seen a single entry FROM clause like 'FROM emps'. See comments
+ // elsewhere regarding <COMMA> lookahead.
+ LOOKAHEAD(3)
Review comment:
so locally, even look ahead 3 is allowed ? if that's the case then indeed the global flag is meaningless
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