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presented with an UNKNOWN-type Var, which can happen in cases where an unknown literal appeared in a subquery. While many such cases will fail later on anyway in the planner, there are some cases where the planner is able to flatten the query and replace the Var by the constant before it has to coerce the union column to the final type. I had added this check in 8.4 to provide earlier/better error detection, but it causes a regression for some cases that worked OK before. Fix by not making the check if the input node is UNKNOWN type and not a Const or Param. If it isn't going to work, it will fail anyway at plan time, with the only real loss being inability to provide an error cursor. Per gripe from Britt Piehler. In passing, rename a couple of variables to remove confusion from an inner scope masking the same variable names in an outer scope.
$PostgreSQL: pgsql/src/backend/parser/README,v 1.10 2008/04/09 01:00:46 momjian Exp $ 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 keywords.c turn keywords into specific tokens gram.y parse the tokens and fill query-type-specific structures analyze.c top level of parse analysis for optimizable queries parse_clause.c handle clauses like WHERE, ORDER BY, GROUP BY, ... parse_coerce.c handle coercing expressions to different data types parse_expr.c handle expressions like col, col + 3, x = 3 or x = 4 parse_oper.c handle operators in expressions parse_agg.c handle aggregates, like SUM(col1), AVG(col2), ... parse_func.c handle functions, table.column and column identifiers parse_node.c create nodes for various structures parse_target.c handle the result list of the query parse_relation.c support routines for tables and column handling parse_type.c support routines for data type handling parse_utilcmd.c parse analysis for utility commands (done at execution time)