fix: add better explain for merge into

src/query/sql/src/planner/format/display_plan.rs

@@ -20,15 +20,18 @@ use common_exception::Result;
 use common_expression::types::DataType;
 use common_expression::types::NumberDataType;
 use common_expression::ROW_ID_COL_NAME;
+use itertools::Itertools;
 
 use crate::binder::ColumnBindingBuilder;
+use crate::format_scalar;
 use crate::optimizer::SExpr;
 use crate::planner::format::display_rel_operator::FormatContext;
 use crate::plans::BoundColumnRef;
 use crate::plans::CreateTablePlan;
 use crate::plans::DeletePlan;
 use crate::plans::EvalScalar;
 use crate::plans::Filter;
+use crate::plans::MergeInto;
 use crate::plans::Plan;
 use crate::plans::RelOperator;
 use crate::plans::ScalarItem;
@@ -110,7 +113,7 @@ impl Plan {
             // Insert
             Plan::Insert(_) => Ok("Insert".to_string()),
             Plan::Replace(_) => Ok("Replace".to_string()),
-            Plan::MergeInto(_) => Ok("MergeInto".to_string()),
+            Plan::MergeInto(merge_into) => format_merge_into(merge_into),
             Plan::Delete(delete) => format_delete(delete),
             Plan::Update(_) => Ok("Update".to_string()),
 
@@ -264,3 +267,88 @@ fn format_create_table(create_table: &CreateTablePlan) -> Result<String> {
         None => Ok("CreateTable".to_string()),
     }
 }
+
+fn format_merge_into(merge_into: &MergeInto) -> Result<String> {
+    // add merge into target_table
+    let table_index = merge_into
+        .meta_data
+        .read()
+        .get_table_index(
+            Some(merge_into.database.as_str()),
+            merge_into.table.as_str(),
+        )
+        .unwrap();
+
+    let table_entry = merge_into.meta_data.read().table(table_index).clone();
+    let target_table_format = FormatContext::Text(format!(
+        "target_table: {}.{}.{}",
+        table_entry.catalog(),
+        table_entry.database(),
+        table_entry.name(),
+    ));
+
+    // add macthed clauses
+    let mut matched_children = Vec::with_capacity(merge_into.matched_evaluators.len());
+    let taregt_schema = table_entry.table().schema();
+    for evaluator in &merge_into.matched_evaluators {
+        let condition_format = evaluator.condition.as_ref().map_or_else(
+            || "condition: None".to_string(),
+            |predicate| format!("condition: {}", format_scalar(predicate)),
+        );
+        if evaluator.update.is_none() {
+            matched_children.push(FormatTreeNode::new(FormatContext::Text(format!(
+                "matched delete: [{}]",
+                condition_format
+            ))));
+        } else {
+            let update_format = evaluator
+                .update
+                .as_ref()
+                .unwrap()
+                .iter()
+                .map(|(field_idx, expr)| {
+                    format!(
+                        "{} = {}",
+                        taregt_schema.field(*field_idx).name(),
+                        format_scalar(expr)
+                    )
+                })
+                .join(",");
+            matched_children.push(FormatTreeNode::new(FormatContext::Text(format!(
+                "matched update: [{},update set {}]",
+                condition_format, update_format
+            ))));
+        }
+    }
+    // add unmacthed clauses
+    let mut unmatched_children = Vec::with_capacity(merge_into.unmatched_evaluators.len());
+    for evaluator in &merge_into.unmatched_evaluators {
+        let condition_format = evaluator.condition.as_ref().map_or_else(
+            || "condition: None".to_string(),
+            |predicate| format!("condition: {}", format_scalar(predicate)),
+        );
+        let insert_schema_format = evaluator
+            .source_schema
+            .fields
+            .iter()
+            .map(|field| field.name())
+            .join(",");
+        let values_format = evaluator.values.iter().map(format_scalar).join(",");
+        let unmatched_format = format!(
+            "insert into ({}) values({})",
+            insert_schema_format, values_format
+        );
+        unmatched_children.push(FormatTreeNode::new(FormatContext::Text(format!(
+            "unmatched insert: [{},{}]",
+            condition_format, unmatched_format
+        ))));
+    }
+    let s_expr = merge_into.input.as_ref();
+    let input_format_child = s_expr.to_format_tree(&merge_into.meta_data);
+    let all_children = [matched_children, unmatched_children, vec![
+        input_format_child,
+    ]]
+    .concat();
+    let res = FormatTreeNode::with_children(target_table_format, all_children).format_pretty()?;
+    Ok(format!("MergeInto:\n{res}"))
+}

tests/sqllogictests/suites/mode/standalone/explain/merge_into.test

@@ -0,0 +1,46 @@
+statement ok
+set enable_experimental_merge_into = 1;
+
+statement ok
+CREATE TABLE employees2 (employee_id INT, employee_name VARCHAR(255),department VARCHAR(255));
+
+statement ok
+CREATE TABLE salaries2 (employee_id INT,salary DECIMAL(10, 2));
+
+statement ok
+INSERT INTO employees2 VALUES(1, 'Alice', 'HR'),(2, 'Bob', 'IT'),(3, 'Charlie', 'Finance'),(4, 'David', 'HR');
+
+statement ok
+INSERT INTO salaries2 VALUES(1, 50000.00),(2, 60000.00);
+
+query TT
+MERGE INTO salaries2 USING (SELECT * FROM employees2) as employees2 ON salaries2.employee_id = employees2.employee_id WHEN MATCHED AND employees2.department = 'HR' THEN UPDATE SET salaries2.salary = salaries2.salary + 1000.00 WHEN MATCHED THEN UPDATE SET salaries2.salary = salaries2.salary + 500.00 WHEN NOT MATCHED THEN INSERT (employee_id, salary) VALUES (employees2.employee_id, 55000.00);
+----
+2 2
+
+query T
+explain MERGE INTO salaries2 USING (SELECT * FROM employees2) as employees2 ON salaries2.employee_id = employees2.employee_id WHEN MATCHED AND employees2.department = 'HR' THEN UPDATE SET salaries2.salary = salaries2.salary + 1000.00 WHEN MATCHED THEN UPDATE SET salaries2.salary = salaries2.salary + 500.00 WHEN NOT MATCHED THEN INSERT (employee_id, salary) VALUES (employees2.employee_id, 55000.00);
+----
+MergeInto:
+target_table: default.default.salaries2
+├── matched update: [condition: eq(employees2.department (#2), 'HR'),update set salary = plus(salaries2.salary (#4), 1000.00)]
+├── matched update: [condition: None,update set salary = plus(salaries2.salary (#4), 500.00)]
+├── unmatched insert: [condition: None,insert into (employee_id,salary) values(CAST(employees2.employee_id (#0) AS Int32 NULL),CAST(55000.00 AS Decimal(10, 2) NULL))]
+└── HashJoin: RIGHT OUTER
+    ├── equi conditions: [eq(salaries2.employee_id (#3), employees2.employee_id (#0))]
+    ├── non-equi conditions: []
+    ├── LogicalGet
+    │   ├── table: default.default.salaries2
+    │   ├── filters: []
+    │   ├── order by: []
+    │   └── limit: NONE
+    └── EvalScalar
+        ├── scalars: [employees2.employee_id (#0), employees2.employee_name (#1), employees2.department (#2)]
+        └── LogicalGet
+            ├── table: default.default.employees2
+            ├── filters: []
+            ├── order by: []
+            └── limit: NONE
+
+statement ok
+set enable_experimental_merge_into = 0;