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In commit 1d97c19a0f748e94 and later c1d9579dd8bf3c92, we extended pull_var_clause's API by adding enum-type arguments. That's sort of a pain to maintain, though, because it means every time we add a new behavior we must touch every last one of the call sites, even if there's a reasonable default behavior that most of them could use. Let's switch over to using a bitmask of flags, instead; that seems more maintainable and might save a nanosecond or two as well. This commit changes no behavior in itself, though I'm going to follow it up with one that does add a new behavior. In passing, remove flatten_tlist(), which has not been used since 9.1 and would otherwise need the same API changes. Removing these enums means that optimizer/tlist.h no longer needs to depend on optimizer/var.h. Changing that caused a number of C files to need addition of #include "optimizer/var.h" (probably we can thank old runs of pgrminclude for that); but on balance it seems like a good change anyway.
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_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)