Reimplement CASE val WHEN compval1 THEN ... WHEN compval2 THEN ... END
Tom Lane <tgl@sss.pgh.pa.us>
Reimplement CASE val WHEN compval1 THEN ... WHEN compval2 THEN ... END so that the 'val' is computed only once, per recent discussion. The speedup is not much when 'val' is just a simple variable, but could be significant for larger expressions. More importantly this avoids issues with multiple evaluations of a volatile 'val', and it allows the CASE expression to be reverse-listed in its original form by ruleutils.c.
Files
| Path | Change | +/− |
|---|---|---|
| src/backend/executor/execQual.c | modified | +49 −3 |
| src/backend/executor/execUtils.c | modified | +4 −1 |
| src/backend/nodes/copyfuncs.c | modified | +18 −1 |
| src/backend/nodes/equalfuncs.c | modified | +13 −1 |
| src/backend/nodes/outfuncs.c | modified | +13 −1 |
| src/backend/nodes/readfuncs.c | modified | +17 −1 |
| src/backend/optimizer/util/clauses.c | modified | +21 −7 |
| src/backend/parser/gram.y | modified | +2 −1 |
| src/backend/parser/parse_expr.c | modified | +38 −24 |
| src/backend/utils/adt/ruleutils.c | modified | +19 −4 |
| src/include/catalog/catversion.h | modified | +2 −2 |
| src/include/nodes/execnodes.h | modified | +6 −1 |
| src/include/nodes/nodes.h | modified | +2 −1 |
| src/include/nodes/primnodes.h | modified | +34 −3 |
| src/pl/plpgsql/src/pl_exec.c | modified | +7 −1 |
| src/test/regress/expected/rules.out | modified | +3 −3 |