feat: add limit push down rule

src/query/sql/src/planner/optimizer/rule/factory.rs

@@ -45,6 +45,7 @@ use crate::optimizer::rule::rewrite::RuleSplitAggregate;
 use crate::optimizer::rule::transform::RuleCommuteJoinBaseTable;
 use crate::optimizer::rule::transform::RuleEagerAggregation;
 use crate::optimizer::rule::transform::RuleLeftExchangeJoin;
+use crate::optimizer::rule::rewrite::RulePushDownLimit;
 use crate::optimizer::rule::RuleID;
 use crate::optimizer::rule::RulePtr;
 use crate::MetadataRef;
@@ -63,6 +64,7 @@ impl RuleFactory {
             RuleID::PushDownFilterScan => Ok(Box::new(RulePushDownFilterScan::new(metadata))),
             RuleID::PushDownFilterSort => Ok(Box::new(RulePushDownFilterSort::new())),
             RuleID::PushDownFilterProjectSet => Ok(Box::new(RulePushDownFilterProjectSet::new())),
+            RuleID::PushDownLimit => Ok(Box::new(RulePushDownLimit::new())),
             RuleID::PushDownLimitUnion => Ok(Box::new(RulePushDownLimitUnion::new())),
             RuleID::PushDownLimitScan => Ok(Box::new(RulePushDownLimitScan::new())),
             RuleID::PushDownSortScan => Ok(Box::new(RulePushDownSortScan::new())),

src/query/sql/src/planner/optimizer/rule/rewrite/mod.rs

@@ -42,6 +42,7 @@ mod rule_push_down_sort_scan;
 mod rule_semi_to_inner_join;
 mod rule_split_aggregate;
 mod rule_try_apply_agg_index;
+mod rule_push_down_limit;
 
 pub use rule_commute_join::RuleCommuteJoin;
 pub use rule_eliminate_eval_scalar::RuleEliminateEvalScalar;
@@ -72,3 +73,4 @@ pub use rule_push_down_sort_scan::RulePushDownSortScan;
 pub use rule_semi_to_inner_join::RuleSemiToInnerJoin;
 pub use rule_split_aggregate::RuleSplitAggregate;
 pub use rule_try_apply_agg_index::RuleTryApplyAggIndex;
+pub use rule_push_down_limit::RulePushDownLimit;

src/query/sql/src/planner/optimizer/rule/rewrite/rule_push_down_limit.rs

@@ -0,0 +1,66 @@
+// Copyright 2021 Datafuse Labs
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::sync::Arc;
+
+use databend_common_exception::Result;
+
+use crate::optimizer::extract::Matcher;
+use crate::optimizer::rule::Rule;
+use crate::optimizer::rule::TransformResult;
+use crate::optimizer::RuleID;
+use crate::optimizer::SExpr;
+use crate::plans::Limit;
+use crate::plans::RelOp;
+use crate::plans::RelOperator;
+use crate::plans::DummyTableScan;
+
+pub struct RulePushDownLimit {
+    id: RuleID,
+    matchers: Vec<Matcher>,
+}
+
+impl RulePushDownLimit {
+    pub fn new() -> Self {
+        Self {
+            id: RuleID::PushDownLimit,
+            matchers: vec![Matcher::MatchOp {
+                op_type: RelOp::Limit,
+                children: vec![Matcher::Leaf],
+            }],
+        }
+    }
+}
+
+impl Rule for RulePushDownLimit {
+    fn id(&self) -> RuleID {
+        self.id
+    }
+
+    fn apply(&self, s_expr: &SExpr, state: &mut TransformResult) -> Result<()> {
+        let limit: Limit = s_expr.plan().clone().try_into()?;
+
+        if let Some(limit_val) = limit.limit &&  limit_val == 0{
+            let dummy_scan = DummyTableScan;
+            let result = SExpr::create_leaf(Arc::new(RelOperator::DummyTableScan(dummy_scan)));
+            state.add_result(result);
+        }
+
+        Ok(())
+    }
+
+    fn matchers(&self) -> &[Matcher] {
+        &self.matchers
+    }
+}

src/query/sql/src/planner/optimizer/rule/rule.rs

@@ -34,6 +34,7 @@ pub static DEFAULT_REWRITE_RULES: LazyLock<Vec<RuleID>> = LazyLock::new(|| {
         RuleID::PushDownFilterUnion,
         RuleID::PushDownFilterAggregate,
         RuleID::PushDownFilterWindow,
+        RuleID::PushDownLimit,
         RuleID::PushDownLimitUnion,
         RuleID::PushDownLimitEvalScalar,
         RuleID::PushDownLimitSort,
@@ -83,6 +84,7 @@ pub enum RuleID {
     PushDownFilterSort,
     PushDownFilterProjectSet,
     PushDownFilterWindow,
+    PushDownLimit,
     PushDownLimitUnion,
     PushDownLimitOuterJoin,
     PushDownLimitEvalScalar,