From 17867e446fc4e31c653a42bcccc071558187ef53 Mon Sep 17 00:00:00 2001
From: minghong <minghong.zhou@163.com>
Date: Thu, 10 Nov 2022 11:25:02 +0800
Subject: [PATCH] [feature](nereids) let user define right deep tree penalty by
 session variable (#14040)

it is hard for us to find a proper factor for all queries.
default is 0.7
---
 .../doris/nereids/cost/CostCalculator.java    | 20 ++++++++++---------
 .../org/apache/doris/qe/SessionVariable.java  | 12 +++++++++++
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/cost/CostCalculator.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/cost/CostCalculator.java
index c3c78396e9..7f5412470c 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/cost/CostCalculator.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/cost/CostCalculator.java
@@ -51,14 +51,7 @@ public class CostCalculator {
     static final double CPU_WEIGHT = 1;
     static final double MEMORY_WEIGHT = 1;
     static final double NETWORK_WEIGHT = 1.5;
-    /**
-     * Except stats information, there are some special criteria in doris.
-     * For example, in hash join cluster, BE could build hash tables
-     * in parallel for left deep tree. And hence, we need to punish right deep tree.
-     * penalyWeight is the factor of punishment.
-     * The punishment is denoted by stats.penalty.
-     */
-    static final double PENALTY_WEIGHT = 0.5;
+
     /**
      * The intuition behind `HEAVY_OPERATOR_PUNISH_FACTOR` is we need to avoid this form of join patterns:
      * Plan1: L join ( AGG1(A) join AGG2(B))
@@ -80,7 +73,16 @@ public class CostCalculator {
         CostEstimator costCalculator = new CostEstimator();
         CostEstimate costEstimate = groupExpression.getPlan().accept(costCalculator, planContext);
         groupExpression.setCostEstimate(costEstimate);
-        CostWeight costWeight = new CostWeight(CPU_WEIGHT, MEMORY_WEIGHT, NETWORK_WEIGHT, PENALTY_WEIGHT);
+        /*
+         * About PENALTY:
+         * Except stats information, there are some special criteria in doris.
+         * For example, in hash join cluster, BE could build hash tables
+         * in parallel for left deep tree. And hence, we need to punish right deep tree.
+         * penalyWeight is the factor of punishment.
+         * The punishment is denoted by stats.penalty.
+         */
+        CostWeight costWeight = new CostWeight(CPU_WEIGHT, MEMORY_WEIGHT, NETWORK_WEIGHT,
+                ConnectContext.get().getSessionVariable().getNereidsCboPenaltyFactor());
         return costWeight.calculate(costEstimate);
     }
 
diff --git a/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java b/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
index 205779b77e..4d7c4a8a80 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/qe/SessionVariable.java
@@ -191,6 +191,8 @@ public class SessionVariable implements Serializable, Writable {
     public static final String ENABLE_NEREIDS_RUNTIME_FILTER = "enable_nereids_runtime_filter";
 
     public static final String NEREIDS_STAR_SCHEMA_SUPPORT = "nereids_star_schema_support";
+
+    public static final String NEREIDS_CBO_PENALTY_FACTOR = "nereids_cbo_penalty_factor";
     public static final String ENABLE_NEREIDS_TRACE = "enable_nereids_trace";
     public static final String ENABLE_NEREIDS_REORDER_TO_ELIMINATE_CROSS_JOIN =
             "enable_nereids_reorder_to_eliminate_cross_join";
@@ -516,6 +518,8 @@ public class SessionVariable implements Serializable, Writable {
     @VariableMgr.VarAttr(name = NEREIDS_STAR_SCHEMA_SUPPORT)
     private boolean nereidsStarSchemaSupport = true;
 
+    @VariableMgr.VarAttr(name = NEREIDS_CBO_PENALTY_FACTOR)
+    private double nereidsCboPenaltyFactor = 0.7;
     @VariableMgr.VarAttr(name = ENABLE_NEREIDS_TRACE)
     private boolean enableNereidsTrace = false;
 
@@ -1103,6 +1107,14 @@ public class SessionVariable implements Serializable, Writable {
         return isEnableNereidsPlanner() && nereidsStarSchemaSupport;
     }
 
+    public double getNereidsCboPenaltyFactor() {
+        return nereidsCboPenaltyFactor;
+    }
+
+    public void setNereidsCboPenaltyFactor(double penaltyFactor) {
+        this.nereidsCboPenaltyFactor = penaltyFactor;
+    }
+
     public boolean isEnableNereidsTrace() {
         return isEnableNereidsPlanner() && enableNereidsTrace;
     }