From 067ede14d8331c8ad2c53d8acf96ef12789bb6f0 Mon Sep 17 00:00:00 2001
From: "zhongjian.xzj" <zhongjian.xzj@zhongjianxzjdeMacBook-Pro.local>
Date: Sat, 14 Sep 2024 17:45:18 +0800
Subject: [PATCH] [opt](nereids) refine expression estimation

---
 .../nereids/stats/ExpressionEstimation.java   | 51 ++++++++++---------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/ExpressionEstimation.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/ExpressionEstimation.java
index 710a01d59b34ce4..578ba1b00446350 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/ExpressionEstimation.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/stats/ExpressionEstimation.java
@@ -41,6 +41,7 @@
 import org.apache.doris.nereids.trees.expressions.VirtualSlotReference;
 import org.apache.doris.nereids.trees.expressions.WhenClause;
 import org.apache.doris.nereids.trees.expressions.functions.BoundFunction;
+import org.apache.doris.nereids.trees.expressions.functions.agg.AggregateFunction;
 import org.apache.doris.nereids.trees.expressions.functions.agg.Avg;
 import org.apache.doris.nereids.trees.expressions.functions.agg.Count;
 import org.apache.doris.nereids.trees.expressions.functions.agg.Max;
@@ -188,6 +189,10 @@ public ColumnStatistic visitIf(If ifClause, Statistics context) {
 
     @Override
     public ColumnStatistic visitCast(Cast cast, Statistics context) {
+        ColumnStatistic stats = context.findColumnStatistics(cast);
+        if (stats != null) {
+            return stats;
+        }
         ColumnStatistic childColStats = cast.child().accept(this, context);
         Preconditions.checkNotNull(childColStats, "childColStats is null");
         return castMinMax(childColStats, cast.getDataType());
@@ -350,10 +355,7 @@ public ColumnStatistic visitMin(Min min, Statistics context) {
             return ColumnStatistic.UNKNOWN;
         }
         // if this is scalar agg, we will update count and ndv to 1 when visiting group clause
-        return new ColumnStatisticBuilder(columnStat)
-                .setMinExpr(null).setMinValue(Double.NEGATIVE_INFINITY)
-                .setMaxExpr(null).setMaxValue(Double.POSITIVE_INFINITY)
-                .build();
+        return new ColumnStatisticBuilder(columnStat).build();
     }
 
     @Override
@@ -364,10 +366,7 @@ public ColumnStatistic visitMax(Max max, Statistics context) {
             return ColumnStatistic.UNKNOWN;
         }
         // if this is scalar agg, we will update count and ndv to 1 when visiting group clause
-        return new ColumnStatisticBuilder(columnStat)
-                .setMinExpr(null).setMinValue(Double.NEGATIVE_INFINITY)
-                .setMaxExpr(null).setMaxValue(Double.POSITIVE_INFINITY)
-                .build();
+        return new ColumnStatisticBuilder(columnStat).build();
     }
 
     @Override
@@ -383,27 +382,13 @@ public ColumnStatistic visitCount(Count count, Statistics context) {
     // TODO: return a proper estimated stat after supports histogram
     @Override
     public ColumnStatistic visitSum(Sum sum, Statistics context) {
-        ColumnStatistic columnStat = sum.child().accept(this, context);
-        if (columnStat.isUnKnown) {
-            return ColumnStatistic.UNKNOWN;
-        }
-        return new ColumnStatisticBuilder(columnStat)
-                .setMinExpr(null).setMinValue(Double.NEGATIVE_INFINITY)
-                .setMaxExpr(null).setMaxValue(Double.POSITIVE_INFINITY)
-                .build();
+        return sum.child().accept(this, context);
     }
 
     // TODO: return a proper estimated stat after supports histogram
     @Override
     public ColumnStatistic visitAvg(Avg avg, Statistics context) {
-        ColumnStatistic columnStat = avg.child().accept(this, context);
-        if (columnStat.isUnKnown) {
-            return ColumnStatistic.UNKNOWN;
-        }
-        return new ColumnStatisticBuilder(columnStat)
-                .setMinExpr(null).setMinValue(Double.NEGATIVE_INFINITY)
-                .setMaxExpr(null).setMaxValue(Double.POSITIVE_INFINITY)
-                .build();
+        return avg.child().accept(this, context);
     }
 
     @Override
@@ -467,6 +452,24 @@ public ColumnStatistic visitAggregateExpression(AggregateExpression aggregateExp
                 .build();
     }
 
+    @Override
+    public ColumnStatistic visitAggregateFunction(AggregateFunction aggregateExpression,
+            Statistics context) {
+        if (aggregateExpression.children().size() == 1) {
+            ColumnStatistic columnStat = aggregateExpression.child(0).accept(this, context);
+            if (columnStat.isUnKnown) {
+                return ColumnStatistic.UNKNOWN;
+            }
+            // by default reset min/max as invalid to avoid misused
+            return new ColumnStatisticBuilder(columnStat)
+                    .setMinExpr(null).setMinValue(Double.NEGATIVE_INFINITY)
+                    .setMaxExpr(null).setMaxValue(Double.POSITIVE_INFINITY)
+                    .build();
+        } else {
+            return visit(aggregateExpression, context);
+        }
+    }
+
     @Override
     public ColumnStatistic visitComparisonPredicate(ComparisonPredicate cp, Statistics context) {
         ColumnStatistic leftStats = cp.left().accept(this, context);