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Tom Lane c6b3c939b7 Make operator precedence follow the SQL standard more closely. ... While the SQL standard is pretty vague on the overall topic of operator precedence (because it never presents a unified BNF for all expressions), it does seem reasonable to conclude from the spec for <boolean value expression> that OR has the lowest precedence, then AND, then NOT, then IS tests, then the six standard comparison operators, then everything else (since any non-boolean operator in a WHERE clause would need to be an argument of one of these). We were only sort of on board with that: most notably, while "<" ">" and "=" had properly low precedence, "<=" ">=" and "<>" were treated as generic operators and so had significantly higher precedence. And "IS" tests were even higher precedence than those, which is very clearly wrong per spec. Another problem was that "foo NOT SOMETHING bar" constructs, such as "x NOT LIKE y", were treated inconsistently because of a bison implementation artifact: they had the documented precedence with respect to operators to their right, but behaved like NOT (i.e., very low priority) with respect to operators to their left. Fixing the precedence issues is just a small matter of rearranging the precedence declarations in gram.y, except for the NOT problem, which requires adding an additional lookahead case in base_yylex() so that we can attach a different token precedence to NOT LIKE and allied two-word operators. The bulk of this patch is not the bug fix per se, but adding logic to parse_expr.c to allow giving warnings if an expression has changed meaning because of these precedence changes. These warnings are off by default and are enabled by the new GUC operator_precedence_warning. It's believed that very few applications will be affected by these changes, but it was agreed that a warning mechanism is essential to help debug any that are.		11 years ago
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.gitignore	Convert cvsignore to gitignore, and add .gitignore for build targets.	16 years ago
analyze.h	Update copyright for 2015	11 years ago
gramparse.h	Improve parser's one-extra-token lookahead mechanism.	11 years ago
keywords.h	Update copyright for 2015	11 years ago
kwlist.h	Update copyright for 2015	11 years ago
parse_agg.h	Update copyright for 2015	11 years ago
parse_clause.h	Update copyright for 2015	11 years ago
parse_coerce.h	Update copyright for 2015	11 years ago
parse_collate.h	Update copyright for 2015	11 years ago
parse_cte.h	Update copyright for 2015	11 years ago
parse_expr.h	Make operator precedence follow the SQL standard more closely.	11 years ago
parse_func.h	Update copyright for 2015	11 years ago
parse_node.h	Update copyright for 2015	11 years ago
parse_oper.h	Update copyright for 2015	11 years ago
parse_param.h	Update copyright for 2015	11 years ago
parse_relation.h	Suggest to the user the column they may have meant to reference.	11 years ago
parse_target.h	Update copyright for 2015	11 years ago
parse_type.h	Update copyright for 2015	11 years ago
parse_utilcmd.h	Update copyright for 2015	11 years ago
parser.h	Update copyright for 2015	11 years ago
parsetree.h	Update copyright for 2015	11 years ago
scanner.h	Make operator precedence follow the SQL standard more closely.	11 years ago
scansup.h	Update copyright for 2015	11 years ago