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According to the SQL/JSON standard, JSON_ARRAY(query) must return an
empty JSON array ('[]') when the subquery returns zero rows.
Previously, the parser rewrote JSON_ARRAY(query) into a JSON_ARRAYAGG
aggregate function. Because this aggregate evaluates to NULL over an
empty set without a GROUP BY clause, the constructor erroneously
returned NULL. Additionally, this premature rewrite baked physical
implementation details into the catalog, preventing ruleutils.c from
deparsing the original syntax for views.
This patch resolves both issues by introducing a new
JSCTOR_JSON_ARRAY_QUERY constructor type. The parser builds the
executable form --- a COALESCE-wrapped JSON_ARRAYAGG subquery --- from
raw parse nodes via transformExprRecurse, and stores it in the func
field. The original transformed Query is kept in a new orig_query
field so that ruleutils.c can deparse the original syntax for views.
During planning, eval_const_expressions replaces the node with the
pre-built func expression.
The deparsing issue was reported by Tom Lane.
Bump catalog version.
Bug: #19418
Reported-by: Lukas Eder <lukas.eder@gmail.com>
Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/19418-591ba1f29862ef5b@postgresql.org
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| .. | ||
| .gitignore | ||
| analyze.c | ||
| check_keywords.pl | ||
| gram.y | ||
| gramparse.h | ||
| Makefile | ||
| meson.build | ||
| parse_agg.c | ||
| parse_clause.c | ||
| parse_coerce.c | ||
| parse_collate.c | ||
| parse_cte.c | ||
| parse_enr.c | ||
| parse_expr.c | ||
| parse_func.c | ||
| parse_graphtable.c | ||
| parse_jsontable.c | ||
| parse_merge.c | ||
| parse_node.c | ||
| parse_oper.c | ||
| parse_param.c | ||
| parse_relation.c | ||
| parse_target.c | ||
| parse_type.c | ||
| parse_utilcmd.c | ||
| parser.c | ||
| README | ||
| scan.l | ||
| scansup.c | ||
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_enr.c handle ephemeral named rels (trigger transition tables, ...) parse_func.c handle functions, table.column and column identifiers parse_jsontable.c handle JSON_TABLE parse_merge.c handle MERGE 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.