From dfa428a809d9a98d7f93093b99af33c616e3b51c Mon Sep 17 00:00:00 2001
From: zhangstar333 <2561612514@qq.com>
Date: Tue, 21 May 2024 23:10:53 +0800
Subject: [PATCH] push down count

---
 .../apache/doris/nereids/rules/RuleType.java  |  1 +
 .../implementation/AggregateStrategies.java   | 49 +++++++++++++++++++
 .../explain/test_pushdown_explain.groovy      |  8 +++
 3 files changed, 58 insertions(+)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/RuleType.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/RuleType.java
index b1101b7592b60cc..f63ae1bca6e0961 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/RuleType.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/RuleType.java
@@ -429,6 +429,7 @@ public enum RuleType {
     STORAGE_LAYER_AGGREGATE_WITH_PROJECT(RuleTypeClass.IMPLEMENTATION),
     STORAGE_LAYER_AGGREGATE_WITHOUT_PROJECT_FOR_FILE_SCAN(RuleTypeClass.IMPLEMENTATION),
     STORAGE_LAYER_AGGREGATE_WITH_PROJECT_FOR_FILE_SCAN(RuleTypeClass.IMPLEMENTATION),
+    STORAGE_LAYER_WITH_PROJECT_NO_SLOT_REF(RuleTypeClass.IMPLEMENTATION),
     STORAGE_LAYER_AGGREGATE_MINMAX_ON_UNIQUE(RuleTypeClass.IMPLEMENTATION),
     STORAGE_LAYER_AGGREGATE_MINMAX_ON_UNIQUE_WITHOUT_PROJECT(RuleTypeClass.IMPLEMENTATION),
     COUNT_ON_INDEX(RuleTypeClass.IMPLEMENTATION),
diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/implementation/AggregateStrategies.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/implementation/AggregateStrategies.java
index e1095df7bab0b97..3b1659d4edbf7e5 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/implementation/AggregateStrategies.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/rules/implementation/AggregateStrategies.java
@@ -215,6 +215,16 @@ public List<Rule> buildRules() {
                 .when(agg -> agg.isNormalized() && enablePushDownNoGroupAgg())
                 .thenApply(ctx -> storageLayerAggregate(ctx.root, null, ctx.root.child(), ctx.cascadesContext))
             ),
+            RuleType.STORAGE_LAYER_WITH_PROJECT_NO_SLOT_REF.build(
+                    logicalProject(
+                            logicalOlapScan()
+                    )
+                    .thenApply(ctx -> {
+                        LogicalProject<LogicalOlapScan> project = ctx.root;
+                        LogicalOlapScan olapScan = project.child();
+                        return pushDownCountWithoutSlotRef(project, olapScan, ctx.cascadesContext);
+                    })
+            ),
             RuleType.STORAGE_LAYER_AGGREGATE_WITH_PROJECT.build(
                 logicalAggregate(
                     logicalProject(
@@ -306,6 +316,45 @@ && couldConvertToMulti(agg))
         );
     }
 
+    /*
+     *  select 66 from baseall_dup; could use pushAggOp=COUNT to not scan real data.
+     */
+    private LogicalProject<? extends Plan> pushDownCountWithoutSlotRef(
+            LogicalProject<? extends Plan> project,
+            LogicalOlapScan logicalScan,
+            CascadesContext cascadesContext) {
+        final LogicalProject<? extends Plan> canNotPush = project;
+        if (!enablePushDownNoGroupAgg()) {
+            return canNotPush;
+        }
+        if (logicalScan != null) {
+            KeysType keysType = logicalScan.getTable().getKeysType();
+            if (keysType != KeysType.DUP_KEYS) {
+                return canNotPush;
+            }
+        }
+        List<Expression> projectExpr = project.getProjects()
+                .stream()
+                .map(p -> p instanceof Alias ? p.child(0) : p)
+                .collect(ImmutableList.toImmutableList());
+        boolean noSlotRef = projectExpr.stream().allMatch(expr -> {
+            if (expr instanceof SlotReference) {
+                return false;
+            }
+            return true;
+        });
+        if (!noSlotRef) {
+            return canNotPush;
+        }
+        PhysicalOlapScan physicalOlapScan
+                = (PhysicalOlapScan) new LogicalOlapScanToPhysicalOlapScan()
+                .build()
+                .transform(logicalScan, cascadesContext)
+                .get(0);
+        return project.withChildren(ImmutableList.of(new PhysicalStorageLayerAggregate(
+                physicalOlapScan, PushDownAggOp.COUNT)));
+    }
+
     private boolean enablePushDownMinMaxOnUnique() {
         ConnectContext connectContext = ConnectContext.get();
         return connectContext != null && connectContext.getSessionVariable().isEnablePushDownMinMaxOnUnique();
diff --git a/regression-test/suites/nereids_p0/explain/test_pushdown_explain.groovy b/regression-test/suites/nereids_p0/explain/test_pushdown_explain.groovy
index f7360963e559a72..1e691f2be9ff527 100644
--- a/regression-test/suites/nereids_p0/explain/test_pushdown_explain.groovy
+++ b/regression-test/suites/nereids_p0/explain/test_pushdown_explain.groovy
@@ -65,6 +65,14 @@ suite("test_pushdown_explain") {
         sql("select count(cast(lo_orderkey as bigint)) from test_lineorder;")
         contains "pushAggOp=COUNT"
     }
+    explain {
+        sql("select 66 from test_lineorder;")
+        contains "pushAggOp=COUNT"
+    }
+    explain {
+        sql("select lo_orderkey from test_lineorder;")
+        contains "pushAggOp=NONE"
+    }
 
     sql "DROP TABLE IF EXISTS table_unique0"
     sql """