vortex-array: stats rewrite predicate satisfiers

Add satisfier rewrites for binary comparisons, boolean composition, and between expressions. The rewrites prove predicates true from min/max stats and add null/NaN guards where comparisons require every row to evaluate true.

Signed-off-by: Nicholas Gates <nick@nickgates.com>

Author: gatesn

vortex-array/src/stats/rewrite/builtins.rs

@@ -130,6 +130,61 @@ impl StatsRewriteRule for BinaryStatsRewrite {
             Operator::Add | Operator::Sub | Operator::Mul | Operator::Div => None,
         })
     }
+
+    fn satisfy(
+        &self,
+        expr: &Expression,
+        ctx: &StatsRewriteCtx<'_>,
+    ) -> VortexResult<Option<Expression>> {
+        let operator = expr.as_::<Binary>();
+        let lhs = expr.child(0);
+        let rhs = expr.child(1);
+
+        // Min/max stats may be truncated to outward bounds (stored min ≤
+        // true min, stored max ≥ true max), which keeps every comparison
+        // below conservative: a bound that proves the predicate proves it
+        // for the true extrema too.
+        let value_predicate = match operator {
+            // Both value ranges pinch to the same single point.
+            Operator::Eq => min(lhs).zip(max(lhs)).zip(min(rhs).zip(max(rhs))).map(
+                |((min_lhs, max_lhs), (min_rhs, max_rhs))| {
+                    and(lt_eq(max_lhs, min_rhs), gt_eq(min_lhs, max_rhs))
+                },
+            ),
+            // The value ranges are disjoint.
+            Operator::NotEq => max(lhs).zip(min(rhs)).zip(min(lhs).zip(max(rhs))).map(
+                |((max_lhs, min_rhs), (min_lhs, max_rhs))| {
+                    or(lt(max_lhs, min_rhs), gt(min_lhs, max_rhs))
+                },
+            ),
+            Operator::Gt => min(lhs).zip(max(rhs)).map(|(a, b)| gt(a, b)),
+            Operator::Gte => min(lhs).zip(max(rhs)).map(|(a, b)| gt_eq(a, b)),
+            Operator::Lt => max(lhs).zip(min(rhs)).map(|(a, b)| lt(a, b)),
+            Operator::Lte => max(lhs).zip(min(rhs)).map(|(a, b)| lt_eq(a, b)),
+            Operator::And => {
+                return Ok(match (ctx.satisfy(lhs)?, ctx.satisfy(rhs)?) {
+                    (Some(lhs), Some(rhs)) => Some(and(lhs, rhs)),
+                    _ => None,
+                });
+            }
+            Operator::Or => {
+                let lhs_satisfier = ctx.satisfy(lhs)?;
+                let rhs_satisfier = ctx.satisfy(rhs)?;
+                return Ok(or_collect(lhs_satisfier.into_iter().chain(rhs_satisfier)));
+            }
+            Operator::Add | Operator::Sub | Operator::Mul | Operator::Div => return Ok(None),
+        };
+        value_predicate
+            .map(|value_predicate| {
+                // Satisfaction must prove more than the values: a NaN
+                // operand makes every comparison false, and a null operand
+                // makes it null — neither is `true`, so the rewrite is only
+                // sound over rows proven non-NaN and non-null.
+                let guarded = with_nan_predicate(ctx, lhs, rhs, value_predicate)?;
+                with_all_non_null_predicate(ctx, [lhs, rhs], guarded)
+            })
+            .transpose()
+    }
 }
 
 #[derive(Debug)]
@@ -154,6 +209,21 @@ impl StatsRewriteRule for BetweenStatsRewrite {
         let rhs = Binary.new_expr(options.upper_strict.to_operator(), [arr, upper]);
         ctx.falsify(&and(lhs, rhs))
     }
+
+    fn satisfy(
+        &self,
+        expr: &Expression,
+        ctx: &StatsRewriteCtx<'_>,
+    ) -> VortexResult<Option<Expression>> {
+        let options = expr.as_::<Between>();
+        let arr = expr.child(0).clone();
+        let lower = expr.child(1).clone();
+        let upper = expr.child(2).clone();
+
+        let lhs = Binary.new_expr(options.lower_strict.to_operator(), [lower, arr.clone()]);
+        let rhs = Binary.new_expr(options.upper_strict.to_operator(), [arr, upper]);
+        ctx.satisfy(&and(lhs, rhs))
+    }
 }
 
 #[derive(Debug)]
@@ -503,6 +573,27 @@ fn with_nan_predicate(
     with_all_non_nan_predicate(ctx, [lhs, rhs], value_predicate)
 }
 
+// Satisfaction rewrites prove a predicate true for *every* row, but min/max
+// stats describe non-null values only: a null operand row evaluates the
+// comparison to null, not true. Guard each nullable operand with an
+// all-non-null check; non-nullable operands need none.
+fn with_all_non_null_predicate<'a>(
+    ctx: &StatsRewriteCtx<'_>,
+    exprs: impl IntoIterator<Item = &'a Expression>,
+    value_predicate: Expression,
+) -> VortexResult<Expression> {
+    let mut null_checks = Vec::new();
+    for expr in exprs {
+        if ctx.return_dtype(expr)?.is_nullable() {
+            null_checks.push(all_non_null(expr));
+        }
+    }
+    Ok(match and_collect(null_checks) {
+        Some(null_check) => and(null_check, value_predicate),
+        None => value_predicate,
+    })
+}
+
 fn with_all_non_nan_predicate<'a>(
     ctx: &StatsRewriteCtx<'_>,
     exprs: impl IntoIterator<Item = &'a Expression>,
@@ -626,6 +717,7 @@ mod tests {
                 ("f", DType::Primitive(PType::F32, Nullability::NonNullable)),
                 ("s", DType::Utf8(Nullability::NonNullable)),
                 ("t", DType::Utf8(Nullability::NonNullable)),
+                ("n", DType::Primitive(PType::I32, Nullability::Nullable)),
             ]),
             Nullability::NonNullable,
         )
@@ -671,6 +763,96 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn rewrites_comparison_satisfier() -> VortexResult<()> {
+        // Non-nullable integer: the value condition alone proves all-true.
+        let expr = lt(col("a"), lit(10));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(lt(stat(col("a"), Stat::Max), lit(10)))
+        );
+
+        let expr = gt_eq(col("a"), lit(10));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(gt_eq(stat(col("a"), Stat::Min), lit(10)))
+        );
+
+        // Column-to-column comparison uses both sides' stats.
+        let expr = lt(col("a"), col("b"));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(lt(stat(col("a"), Stat::Max), stat(col("b"), Stat::Min)))
+        );
+
+        // Floats must also prove no NaNs: a NaN row never satisfies a
+        // comparison.
+        let expr = gt(col("f"), lit(1.0f32));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(and(
+                nan_free(col("f")),
+                gt(stat(col("f"), Stat::Min), lit(1.0f32))
+            ))
+        );
+
+        // Nullable operands must also prove no nulls: a null row evaluates
+        // the comparison to null, not true.
+        let expr = lt(col("n"), lit(10));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(and(
+                all_non_null(&col("n")),
+                lt(stat(col("n"), Stat::Max), lit(10))
+            ))
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn rewrites_boolean_satisfiers() -> VortexResult<()> {
+        // Conjunctions require both satisfiers; disjunctions accept either.
+        let expr = and(gt(col("a"), lit(10)), lt(col("a"), lit(50)));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(and(
+                gt(stat(col("a"), Stat::Min), lit(10)),
+                lt(stat(col("a"), Stat::Max), lit(50)),
+            ))
+        );
+
+        let expr = or(gt(col("a"), lit(10)), lt(col("a"), lit(0)));
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(or(
+                gt(stat(col("a"), Stat::Min), lit(10)),
+                lt(stat(col("a"), Stat::Max), lit(0)),
+            ))
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn rewrites_between_satisfier() -> VortexResult<()> {
+        let expr = between(
+            col("a"),
+            lit(10),
+            lit(50),
+            BetweenOptions {
+                lower_strict: StrictComparison::NonStrict,
+                upper_strict: StrictComparison::NonStrict,
+            },
+        );
+        assert_eq!(
+            satisfy(&expr)?,
+            Some(and(
+                lt_eq(lit(10), stat(col("a"), Stat::Min)),
+                lt_eq(stat(col("a"), Stat::Max), lit(50)),
+            ))
+        );
+        Ok(())
+    }
+
     #[test]
     fn rewrites_boolean_falsifiers() -> VortexResult<()> {
         let expr = and(gt(col("a"), lit(10)), lt(col("a"), lit(50)));