dossett commented on code in PR #3666:
URL: https://github.com/apache/iceberg-python/pull/3666#discussion_r3770759748
##########
pyiceberg/expressions/visitors.py:
##########
@@ -1985,6 +1970,46 @@ def visit_unbound_predicate(self, predicate:
UnboundPredicate) -> BooleanExpress
return bound
+class ResidualVisitor:
+ """Find residuals for an expression using partition values.
+
+ A residual expression is made by partially evaluating an expression using
partition values.
+ For example, if a table is partitioned by day(utc_timestamp) and is read
with a filter expression
+ utc_timestamp > a and utc_timestamp < b, then there are 4 possible
residual expressions
+ for the partition data, d:
+
+ 1. If d > day(a) and d < day(b), the residual is always true
+ 2. If d == day(a) and d != day(b), the residual is utc_timestamp > a
+ 3. If d == day(b) and d != day(a), the residual is utc_timestamp < b
+ 4. If d == day(a) == day(b), the residual is utc_timestamp > a and
utc_timestamp < b
+ """
+
+ schema: Schema
+ spec: PartitionSpec
+ case_sensitive: bool
+ expr: BooleanExpression
+ partition_schema: Schema
+
+ def __init__(self, schema: Schema, spec: PartitionSpec, case_sensitive:
bool, expr: BooleanExpression) -> None:
+ self.schema = schema
+ self.spec = spec
+ self.case_sensitive = case_sensitive
+ self.expr = expr
+ self.partition_schema = Schema(*spec.partition_type(schema).fields)
+
+ def eval(self, partition_data: Record) -> BooleanExpression:
+ return visit(
+ self.expr,
+ visitor=_ResidualEvaluationVisitor(
Review Comment:
It is recreated in the case of cache misses, but the visitor is fairly
lightweight. There's still a net win because the heaviest work (building the
partition `StructType`) is now done once per partition spec in the now
immutable `ResidualEvaluator`. That's a net savings even when there are no
repeated values and no cache hits, per the performance measurement code I ran
(that's in the third commit).
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