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The current implementation fires an AFTER ROW trigger for each tuple that looks like it might be non-unique according to the index contents at the time of insertion. This works well as long as there aren't many conflicts, but won't scale to massive unique-key reassignments. Improving that case is a TODO item. Dean Rasheed
$PostgreSQL: pgsql/src/backend/parser/README,v 1.10 2008/04/09 01:00:46 momjian Exp $ 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 keywords.c turn keywords into specific tokens gram.y parse the tokens and fill query-type-specific structures analyze.c top level of parse analysis for optimizable queries parse_clause.c handle clauses like WHERE, ORDER BY, GROUP BY, ... parse_coerce.c handle coercing expressions to different data types parse_expr.c handle expressions like col, col + 3, x = 3 or x = 4 parse_oper.c handle operators in expressions parse_agg.c handle aggregates, like SUM(col1), AVG(col2), ... parse_func.c handle functions, table.column and column identifiers parse_node.c create nodes for various structures parse_target.c handle the result list of the query parse_relation.c support routines for tables and column handling parse_type.c support routines for data type handling parse_utilcmd.c parse analysis for utility commands (done at execution time)