72cfc17aef
This patch causes unknown-type Consts to be coerced to the resolved output type of the set operation at parse time. Formerly such Consts were left alone until late in the planning stage. The disadvantage of that approach is that it disables some optimizations, because the planner sees the set-op leaf query as having different output column types than the overall set-op. We saw an example of that in a recent performance gripe from Claudio Freire. Fixing such a Const requires scribbling on the leaf query in transformSetOperationTree, but that should be all right since if the leaf query's semantics depended on that output column, it would already have resolved the unknown to something else. Most of the bulk of this patch is a simple adjustment of transformSetOperationTree's API so that upper levels can get at the TargetEntry containing a Const to be replaced: it now returns a list of TargetEntries, instead of just the bare expressions. |
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| .. | ||
| .gitignore | ||
| Makefile | ||
| README | ||
| analyze.c | ||
| gram.y | ||
| keywords.c | ||
| kwlookup.c | ||
| parse_agg.c | ||
| parse_clause.c | ||
| parse_coerce.c | ||
| parse_cte.c | ||
| parse_expr.c | ||
| parse_func.c | ||
| parse_node.c | ||
| parse_oper.c | ||
| parse_param.c | ||
| parse_relation.c | ||
| parse_target.c | ||
| parse_type.c | ||
| parse_utilcmd.c | ||
| parser.c | ||
| scan.l | ||
| scansup.c | ||
README
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)