Cache the scope name prefix to prevent scope traversal in a tight loop #708
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@@ Coverage Diff @@
## main #708 +/- ##
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Coverage 94.80% 94.80%
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Files 247 247
Lines 25701 25711 +10
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+ Hits 24365 24375 +10
Misses 1336 1336
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lpetre
commented
Jun 20, 2022
| @@ -667,6 +657,7 @@ def __init__( | |||
| self.name = name | |||
| self.node = node | |||
| self._scope_overwrites = {} | |||
| self._name_prefix = self._make_name_prefix() | |||
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Pyre is unhappy with this line. Any suggestions @zsol
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Seems like a bug to me, might be worth raising with Pyre folks internally
zsol
approved these changes
Jun 20, 2022
libcst/metadata/scope_provider.py
Outdated
| return {QualifiedName(".".join(parts), QualifiedNameSource.LOCAL)} | ||
| return { | ||
| QualifiedName( | ||
| ".".join(filter(None, [self.scope._name_prefix, full_name])), |
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Neither of these can be None, and this is a pretty hot function. This should be much faster
Suggested change
| ".".join(filter(None, [self.scope._name_prefix, full_name])), | |
| f"{self.scope._name_prefix}.{full_name}", |
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The filter(None,...) also removes empty strings, which is what I need here. Happy to consider other ways to do it.
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f"{a}.{b}" if a else b is about 4x faster still
| @@ -667,6 +657,7 @@ def __init__( | |||
| self.name = name | |||
| self.node = node | |||
| self._scope_overwrites = {} | |||
| self._name_prefix = self._make_name_prefix() | |||
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Seems like a bug to me, might be worth raising with Pyre folks internally
|
Maybe worth putting a |
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0.4.7 - 2022-07-12 Fixed * Fix get_qualified_names_for matching on prefixes of the given name by @lpetre in Instagram/LibCST#719 Added * Implement lazy loading mechanism for expensive metadata providers by @Chenguang-Zhu in Instagram/LibCST#720 0.4.6 - 2022-07-04 New Contributors - @superbobry made their first contribution in Instagram/LibCST#702 Fixed - convert_type_comments now preserves comments following type comments by @superbobry in Instagram/LibCST#702 - QualifiedNameProvider optimizations - Cache the scope name prefix to prevent scope traversal in a tight loop by @lpetre in Instagram/LibCST#708 - Faster qualified name formatting by @lpetre in Instagram/LibCST#710 - Prevent unnecessary work in Scope.get_qualified_names_for_ by @lpetre in Instagram/LibCST#709 - Fix parsing of parenthesized empty tuples by @zsol in Instagram/LibCST#712 - Support whitespace after ParamSlash by @zsol in Instagram/LibCST#713 - [parser] bail on deeply nested expressions by @zsol in Instagram/LibCST#718 0.4.5 - 2022-06-17 New Contributors - @zzl0 made their first contribution in Instagram/LibCST#704 Fixed - Only skip supported escaped characters in f-strings by @zsol in Instagram/LibCST#700 - Escaping quote characters in raw string literals causes a tokenizer error by @zsol in Instagram/LibCST#668 - Corrected a code example in the documentation by @zzl0 in Instagram/LibCST#703 - Handle multiline strings that start with quotes by @zzl0 in Instagram/LibCST#704 - Fixed a performance regression in libcst.metadata.ScopeProvider by @lpetre in Instagram/LibCST#698 0.4.4 - 2022-06-13 New Contributors - @adamchainz made their first contribution in Instagram/LibCST#688 Added - Add package links to PyPI by @adamchainz in Instagram/LibCST#688 - native: add overall benchmark by @zsol in Instagram/LibCST#692 - Add support for PEP-646 by @zsol in Instagram/LibCST#696 Updated - parser: use references instead of smart pointers for Tokens by @zsol in Instagram/LibCST#691
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Summary
We don't need to recompute this name prefix every time we try to lookup a qualified name for a node. This value is immutable when the scope is constructed.
Context
There is a certain type of file that causes the scope provider to take an extraordinary amount of time.
These files tend to fit a specific pattern:
Here is an example: https://github.com/FreeOpcUa/python-opcua/blob/0.98.11/opcua/server/standard_address_space/standard_address_space_part9.py
I've been running these w/ yappi to figure out where the scope provider might be improved.
Test Plan
Previously this file would take ~70 seconds on my laptop (Apple M1 Pro, 32GB RAM). Now it takes ~30 seconds.
Here is the top hits from yappi (sorted by tsub) before and after:
Before
After