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This commit adds columns amoppurpose and amopsortfamily to pg_amop, and column amcanorderbyop to pg_am. For the moment all the entries in amcanorderbyop are "false", since the underlying support isn't there yet. Also, extend the CREATE OPERATOR CLASS/ALTER OPERATOR FAMILY commands with [ FOR SEARCH | FOR ORDER BY sort_operator_family ] clauses to allow the new columns of pg_amop to be populated, and create pg_dump support for dumping that information. I also added some documentation, although it's perhaps a bit premature given that the feature doesn't do anything useful yet. Teodor Sigaev, Robert Haas, Tom Lane
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 kwlookup.c turn keywords into specific tokens keywords.c table of standard keywords (passed to kwlookup.c) 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_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)