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postgresql/src/backend/parser
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Andrew Gierth a40631a920 Fix lexing of standard multi-character operators in edge cases. 
Commits c6b3c939b (which fixed the precedence of >=, <=, <> operators)
and 865f14a2d (which added support for the standard => notation for
named arguments) created a class of lexer tokens which look like
multi-character operators but which have their own token IDs distinct
from Op. However, longest-match rules meant that following any of
these tokens with another operator character, as in (1<>-1), would
cause them to be incorrectly returned as Op.

The error here isn't immediately obvious, because the parser would
usually still find the correct operator via the Op token, but there
were more subtle problems:

1. If immediately followed by a comment or +-, >= <= <> would be given
   the old precedence of Op rather than the correct new precedence;

2. If followed by a comment, != would be returned as Op rather than as
   NOT_EQUAL, causing it not to be found at all;

3. If followed by a comment or +-, the => token for named arguments
   would be lexed as Op, causing the argument to be mis-parsed as a
   simple expression, usually causing an error.

Fix by explicitly checking for the operators in the {operator} code
block in addition to all the existing special cases there.

Backpatch to 9.5 where the problem was introduced.

Analysis and patch by me; review by Tom Lane.
Discussion: https://postgr.es/m/87va851ppl.fsf@news-spur.riddles.org.uk
 		2018-08-23 21:42:40 +01:00
..
.gitignore Convert cvsignore to gitignore, and add .gitignore for build targets. 2010-09-22 12:57:04 +02:00
Makefile Revert MERGE patch 2018-04-12 11:22:56 +01:00
README Move keywords.c/kwlookup.c into src/common/. 2016-03-23 20:22:08 -04:00
analyze.c Fix INSERT ON CONFLICT UPDATE through a view that isn't just SELECT *. 2018-08-04 19:38:58 -04:00
check_keywords.pl Don't fall off the end of perl functions 2018-05-27 09:08:42 -04:00
gram.y Change PROCEDURE to FUNCTION in CREATE TRIGGER syntax 2018-08-22 14:44:49 +02:00
parse_agg.c Revert MERGE patch 2018-04-12 11:22:56 +01:00
parse_clause.c Fix bugs with degenerate window ORDER BY clauses in GROUPS/RANGE mode. 2018-07-11 12:07:20 -04:00
parse_coerce.c Merge catalog/pg_foo_fn.h headers back into pg_foo.h headers. 2018-04-08 14:35:29 -04:00
parse_collate.c Revert MERGE patch 2018-04-12 11:22:56 +01:00
parse_cte.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
parse_enr.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
parse_expr.c Revert MERGE patch 2018-04-12 11:22:56 +01:00
parse_func.c Fix misc typos, mostly in comments. 2018-07-18 16:17:32 +03:00
parse_node.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
parse_oper.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
parse_param.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
parse_relation.c Revert MERGE patch 2018-04-12 11:22:56 +01:00
parse_target.c Indexes with INCLUDE columns and their support in B-tree 2018-04-07 23:00:39 +03:00
parse_type.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
parse_utilcmd.c Improve two error messages 2018-07-12 12:35:59 +02:00
parser.c Update copyright for 2018 2018-01-02 23:30:12 -05:00
scan.l Fix lexing of standard multi-character operators in edge cases. 2018-08-23 21:42:40 +01:00
scansup.c Update copyright for 2018 2018-01-02 23:30:12 -05:00

README 

src/backend/parser/README

Parser
======

This directory does more than tokenize and parse SQL queries.  It also
creates Query structures for the various complex queries that are passed
to the optimizer and then executor.

parser.c	things start here
scan.l		break query into tokens
scansup.c	handle escapes in input strings
gram.y		parse the tokens and produce a "raw" parse tree
analyze.c	top level of parse analysis for optimizable queries
parse_agg.c	handle aggregates, like SUM(col1),  AVG(col2), ...
parse_clause.c	handle clauses like WHERE, ORDER BY, GROUP BY, ...
parse_coerce.c	handle coercing expressions to different data types
parse_collate.c	assign collation information in completed expressions
parse_cte.c	handle Common Table Expressions (WITH clauses)
parse_expr.c	handle expressions like col, col + 3, x = 3 or x = 4
parse_func.c	handle functions, table.column and column identifiers
parse_node.c	create nodes for various structures
parse_oper.c	handle operators in expressions
parse_param.c	handle Params (for the cases used in the core backend)
parse_relation.c support routines for tables and column handling
parse_target.c	handle the result list of the query
parse_type.c	support routines for data type handling
parse_utilcmd.c	parse analysis for utility commands (done at execution time)

See also src/common/keywords.c, which contains the table of standard
keywords and the keyword lookup function.  We separated that out because
various frontend code wants to use it too.