englefly opened a new pull request, #69641:
URL: https://github.com/apache/doris/pull/69641
### What problem does this PR solve?
Issue Number: N/A
Problem Summary:
`test_pushdown_explain` asserts that the plan of
`select count(1) - count(lo_shipmode) from test_lineorder` contains
`pushAggOp=COUNT`. `lo_shipmode` is NOT NULL, so this expression is always 0.
`RewriteSimpleAggToConstantRule` can replace both counts with the table row
count from `SimpleAggCacheMgr` and fold the whole expression into a constant
`VUNION` plan before the scan-level COUNT pushdown happens. The row count is
loaded asynchronously, so whether the rule fires depends on whether the cache
has been warmed by the preceding statements. The assertion can therefore pass
or fail depending on statement timing, and the failure can land on the second
or the third count assertion.
Master's `query_p0/explain/test_pushdown_explain.groovy` already disables
this
rule before the count assertions. This patch aligns the branch-4.1 test with
master so the case keeps testing the COUNT pushdown path instead of the
metadata constant rewrite. The query result is unchanged; this is a test
stabilization, not a planner behavior change.
### Release note
None
### Check List (For Author)
- Test: Manual test on a local branch-4.1 (4.1.5) cluster. With
`SET disable_nereids_rules='REWRITE_SIMPLE_AGG_TO_CONSTANT'`, `count(1)`,
`count(*)` and `count(1) - count(lo_shipmode)` all explain with
`pushAggOp=COUNT`; without the setting the last query folded to a `VUNION`
constant 0 once the row-count cache was warm.
- Behavior changed: No
- Does this need documentation: No
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