On 8/26/25 20:26, Tom Lane wrote:
Richard Guo <[email protected]> writes:
We could then use this function to remove expressions that are known
constant from semi_rhs_exprs. And if we find that all expressions
in semi_rhs_exprs are known constant (the second loose end you
mentioned), we can give up building unique paths and fall back to a
traditional JOIN_SEMI.
Yeah, I was thinking we could just use the paths of the existing
rel, but really this case means that we'd need to de-dup down
to a single row. We could maybe do something involving plastering
LIMIT 1 on top of each input path
Unique node over incoming empty rows seems to act as LIMIT 1, in
particular, it breaks subplan execution after extracting the first row.
Then I see v3 patch covers this case perfectly.
--
Best regard,
Maksim Milyutin
