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If an aggregate function call contains a sub-select that has an RTE referencing a CTE outside the aggregate, we must treat that reference like a Var referencing the CTE's query level for purposes of determining the aggregate's level. Otherwise we might reach the nonsensical conclusion that the aggregate should be evaluated at some query level higher than the CTE, ending in a planner error or a broken plan tree that causes executor failures. Bug: #19055 Reported-by: BugForge <dllggyx@outlook.com> Author: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/19055-6970cfa8556a394d@postgresql.org Backpatch-through: 13
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.