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These commands allow the argument type list to be omitted if there is just one object that matches by name. However, if that syntax was used with DROP IF EXISTS and there was more than one match, you got a "function ... does not exist, skipping" notice message rather than a truthful complaint about the ambiguity. This was basically due to poor factorization and a rats-nest of logic, so refactor the relevant lookup code to make it cleaner. Note that this amounts to narrowing the scope of which sorts of error conditions IF EXISTS will bypass. Per discussion, we only intend it to skip no-such-object cases, not multiple-possible-matches cases. Per bug #15572 from Ash Marath. Although this definitely seems like a bug, it's not clear that people would thank us for changing the behavior in minor releases, so no back-patch. David Rowley, reviewed by Julien Rouhaud and Pavel Stehule Discussion: https://postgr.es/m/15572-ed1b9ed09503de8a@postgresql.org
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.