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Formerly, when trying to copy both indexes and comments, CREATE TABLE LIKE had to pre-assign names to indexes that had comments, because it made up an explicit CommentStmt command to apply the comment and so it had to know the name for the index. This creates bad interactions with other indexes, as shown in bug #6734 from Daniele Varrazzo: the preassignment logic couldn't take any other indexes into account so it could choose a conflicting name. To fix, add a field to IndexStmt that allows it to carry a comment to be assigned to the new index. (This isn't a user-exposed feature of CREATE INDEX, only an internal option.) Now we don't need preassignment of index names in any situation. I also took the opportunity to refactor DefineIndex to accept the IndexStmt as such, rather than passing all its fields individually in a mile-long parameter list. Back-patch to 9.2, but no further, because it seems too dangerous to change IndexStmt or DefineIndex's API in released branches. The bug exists back to 9.0 where CREATE TABLE LIKE grew the ability to copy comments, but given the lack of prior complaints we'll just let it go unfixed before 9.2.
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)