ResultSet set expression API limits size of unions and intersections
Bug #242813 reported by
James Henstridge
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| Storm |
Fix Released
|
Low
|
James Henstridge | ||
Bug Description
The set expression API of ResultSet allows you to combine two result sets together. However, using it multiple times results in expression object hierarchies like Union(Union(
It'd be nice if the ResultSet level API made it possible to generate an expression object like Union(select1, select2, select3, select4, ...) for such cases, which would not hit the same recursion problems.
This applies for Union and Intersection, but maybe not Except (which really is a binary op).
Related branches
lp:~jamesh/storm/bug-242813
- Jamu Kakar (community): Approve
-
Diff: 132 lines2 files modifiedstorm/expr.py (+10/-0)
tests/expr.py (+87/-0)
| Changed in storm: | |
| importance: | Undecided → Low |
Revision history for this message
| James Henstridge (jamesh) wrote | #1 |
| Changed in storm: | |
| assignee: | nobody → James Henstridge (jamesh) |
| milestone: | none → 0.16 |
Revision history for this message
| James Henstridge (jamesh) wrote | #2 |
| Changed in storm: | |
| status: | New → Fix Committed |
| Changed in storm: | |
| status: | Fix Committed → Fix Released |
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I think I am wrong about the API being a limiting factor here: with smarter code, we could pretty easily avoid the recursion problems by changing Store._set_expr() to something like this:
...
left_select = self._get_select()
right_select = other._get_select()
# Try to flatten nested set expressions.
if (isinstance(
subexprs = left_select.exprs + (right_select,)
else:
subexprs = (left_select, right_select)
expr = expr_cls(*subexprs, all=all)
...
The idea being to take advantage of left associativity of set operations to generate a shallower expression tree. It looks like this would bring the same benefit to the SQLObject compatibility layer with no changes.