sql.py: index_cols(): Fixed bug where index columns were sorted by their position in the table, not their position in the index. This was causing the order of columns in covering indexes not to match their order in the corresponding output table index, preventing merge joins and slowing down joins because of the need to do a seq scan. Refactored to use pg_get_indexdef() on each column position index and parsing the result with parse_expr_col(), which greatly simplifies the query and automatically provides the correct sort order.
sql.py: index_cols(): Fixed bug where index columns were sorted by their position in the table, not their position in the index. This was causing the order of columns in covering indexes not to match their order in the corresponding output table index, preventing merge joins and slowing down joins because of the need to do a seq scan. Refactored to use pg_get_indexdef() on each column position index and parsing the result with parse_expr_col(), which greatly simplifies the query and automatically provides the correct sort order.