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1. Remove the special case handling when casting the JsonBehavior expressions to types with typmod, like 86d33987 did for the casting of SQL/JSON constructor functions. 2. Fix casting for fixed-length character and bit string types by using assignment-level casts. This is again similar to what 86d33987 did, but for ON ERROR / EMPTY expressions. 3. Use runtime coercion for the boolean ON ERROR constants so that using fixed-length character string types, for example, for an EXISTS column doesn't cause a "value too long for type character(n)" when the parser tries to coerce the default ON ERROR value "false" to that type, that is, even when clause is not specified. 4. Simplify the conditions of when to use runtime coercion vs creating the cast expression in the parser itself. jsonb-valued expressions are now always coerced at runtime and boolean expressions too if the target type is a string type for the reasons mentioned above. New tests are from a patch that Jian He posted. Outputs of some existing tests change because the coercion now happens at runtime instead of at parse time. Reported-by: Jian He <jian.universality@gmail.com> Author: Jian He <jian.universality@gmail.com> Author: Amit Langote <amitlangote09@gmail.com> Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com Backpatch-through: 17
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_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.