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perf: seed component decls so cold loads avoid Θ(n²) tree walks #34068

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perf: seed component decls so cold loads avoid Θ(n²) tree walks #34068

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perf: O(n) component decl tree lookups via seed on first walk
ljodea Jul 31, 2026
afe98d2
test: assert single component-decl tree materialization on cold load
ljodea Jul 31, 2026
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test: assert single component-decl tree materialization on cold load 
Tighten the call-count check so near-quadratic cold loads cannot pass.
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@ljodea
ljodea committed Jul 31, 2026
commit afe98d266a8e9aaa116d10eefec42991c01ea0b1
11 changes: 5 additions & 6 deletions ...r/dagster_tests/components_tests/component_tree_tests/test_component_decl_tree_caching.py
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Expand Up @@ -53,13 +53,12 @@ def counting_component_decl_tree(self: ComponentTree):
):
tree.build_defs()

# One materialization is enough to seed cacheable child decls for
# the rest of the load. A few more is fine if root / path lookup
# paths need a second pass; once-per-sibling is not.
assert call_count < n_siblings, (
# One materialization seeds cacheable child decls for the rest of
# the load. A looser bound (e.g. call_count < n) would still pass
# near-quadratic cold loads and miss regressions.
assert call_count == 1, (
f"_component_decl_tree was called {call_count} times for "
f"{n_siblings} sibling components (expected O(1) materializations, "
f"not once per component)"
f"{n_siblings} sibling components (expected one materialization)"
)


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