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postgresql/src/backend/parser
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Tom Lane 5ee190f8ec Rationalize use of list_concat + list_copy combinations. 
In the wake of commit 1cff1b95a, the result of list_concat no longer
shares the ListCells of the second input.  Therefore, we can replace
"list_concat(x, list_copy(y))" with just "list_concat(x, y)".

To improve call sites that were list_copy'ing the first argument,
or both arguments, invent "list_concat_copy()" which produces a new
list sharing no ListCells with either input.  (This is a bit faster
than "list_concat(list_copy(x), y)" because it makes the result list
the right size to start with.)

In call sites that were not list_copy'ing the second argument, the new
semantics mean that we are usually leaking the second List's storage,
since typically there is no remaining pointer to it.  We considered
inventing another list_copy variant that would list_free the second
input, but concluded that for most call sites it isn't worth worrying
about, given the relative compactness of the new List representation.
(Note that in cases where such leakage would happen, the old code
already leaked the second List's header; so we're only discussing
the size of the leak not whether there is one.  I did adjust two or
three places that had been troubling to free that header so that
they manually free the whole second List.)

Patch by me; thanks to David Rowley for review.

Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
2019-08-12 11:20:18 -04:00
..
.gitignore Convert cvsignore to gitignore, and add .gitignore for build targets. 2010-09-22 12:57:04 +02:00
analyze.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
check_keywords.pl Update copyright for 2019 2019-01-02 12:44:25 -05:00
gram.y Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
Makefile Revert MERGE patch 2018-04-12 11:22:56 +01:00
parse_agg.c Rationalize use of list_concat + list_copy combinations. 2019-08-12 11:20:18 -04:00
parse_clause.c Rationalize use of list_concat + list_copy combinations. 2019-08-12 11:20:18 -04:00
parse_coerce.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
parse_collate.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
parse_cte.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
parse_enr.c Update copyright for 2019 2019-01-02 12:44:25 -05:00
parse_expr.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
parse_func.c Require the schema qualification in pg_temp.type_name(arg). 2019-08-05 07:48:41 -07:00
parse_node.c Reconcile nodes/*funcs.c with PostgreSQL 12 work. 2019-06-09 14:00:36 -07:00
parse_oper.c Fix inconsistencies and typos in the tree, take 9 2019-08-05 12:14:58 +09:00
parse_param.c Phase 2 pgindent run for v12. 2019-05-22 13:04:48 -04:00
parse_relation.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
parse_target.c Represent Lists as expansible arrays, not chains of cons-cells. 2019-07-15 13:41:58 -04:00
parse_type.c Require the schema qualification in pg_temp.type_name(arg). 2019-08-05 07:48:41 -07:00
parse_utilcmd.c Add comment on no default partition with hash partitioning 2019-08-07 12:27:47 -04:00
parser.c Replace the data structure used for keyword lookup. 2019-01-06 17:02:57 -05:00
README Move keywords.c/kwlookup.c into src/common/. 2016-03-23 20:22:08 -04:00
scan.l Replace the data structure used for keyword lookup. 2019-01-06 17:02:57 -05:00
scansup.c Update copyright for 2019 2019-01-02 12:44:25 -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.