Merge pull request #9406 from sandflee/limit2

feat(query): add max_query_row_nums

src/query/service/tests/it/storages/testdata/settings_table.txt

@@ -17,6 +17,7 @@ DB.Table: 'system'.'settings', Table: settings-table_id:1, ver:0, Engine: System
 | max_block_size                     | 65536      | 65536       | SESSION | Maximum block size for reading, default value: 65536.                                                                                                                                                                                   | UInt64 |
 | max_execute_time                   | 0          | 0           | SESSION | The maximum query execution time. it means no limit if the value is zero. default value: 0.                                                                                                                                             | UInt64 |
 | max_inlist_to_or                   | 3          | 3           | SESSION | Max size in inlist expression that will convert to or combinator, default value: 3.                                                                                                                                                     | UInt64 |
+| max_result_rows                    | 0          | 0           | SESSION | Auto limit max result rows if user not specify the limit, default is 0 means no limit                                                                                                                                                   | UInt64 |
 | parquet_uncompressed_buffer_size   | 2097152    | 2097152     | SESSION | Parquet decompresses buffer size. default: 2MB                                                                                                                                                                                          | UInt64 |
 | prefer_broadcast_join              | 0          | 0           | SESSION | If enable broadcast join, default value: 0                                                                                                                                                                                              | UInt64 |
 | quoted_ident_case_sensitive        | 1          | 1           | SESSION | Case sensitivity of quoted identifiers, default value: 1 (aka case-sensitive).                                                                                                                                                          | UInt64 |

src/query/settings/src/lib.rs

@@ -388,6 +388,13 @@ impl Settings {
                 desc: "the max number of rows each read from parquet to databend processor",
                 possible_values: None,
             },
+            SettingValue {
+                default_value: UserSettingValue::UInt64(0),
+                user_setting: UserSetting::create("max_result_rows", UserSettingValue::UInt64(0)),
+                level: ScopeLevel::Session,
+                desc: "Auto limit max result rows if user not specify the limit, default is 0 means no limit",
+                possible_values: None,
+            },
             SettingValue {
                 default_value: UserSettingValue::UInt64(1),
                 user_setting: UserSetting::create(
@@ -685,6 +692,12 @@ impl Settings {
         Ok(v != 0)
     }
 
+    pub fn get_max_result_rows(&self) -> Result<u64> {
+        static KEY: &str = "max_result_rows";
+        let v = self.try_get_u64(KEY)?;
+        Ok(v)
+    }
+
     pub fn set_enable_distributed_eval_index(&self, val: bool) -> Result<()> {
         static KEY: &str = "enable_distributed_eval_index";
         let v = u64::from(val);

src/query/sql/src/planner/binder/select.rs

@@ -19,6 +19,7 @@ use common_ast::ast::Expr;
 use common_ast::ast::Join;
 use common_ast::ast::JoinCondition;
 use common_ast::ast::JoinOperator;
+use common_ast::ast::Literal;
 use common_ast::ast::OrderByExpr;
 use common_ast::ast::Query;
 use common_ast::ast::SelectStmt;
@@ -227,6 +228,15 @@ impl<'a> Binder {
             }
         };
 
+        let default_limit = if self.ctx.get_settings().get_max_result_rows()? > 0 {
+            Some(Expr::Literal {
+                span: &[],
+                lit: Literal::Integer(self.ctx.get_settings().get_max_result_rows()?),
+            })
+        } else {
+            None
+        };
+
         if !query.limit.is_empty() {
             if query.limit.len() == 1 {
                 s_expr = self
@@ -244,7 +254,11 @@ impl<'a> Binder {
             }
         } else if query.offset.is_some() {
             s_expr = self
-                .bind_limit(&bind_context, s_expr, None, &query.offset)
+                .bind_limit(&bind_context, s_expr, default_limit.as_ref(), &query.offset)
+                .await?;
+        } else if let Some(l) = default_limit {
+            s_expr = self
+                .bind_limit(&bind_context, s_expr, Some(&l), &None)
                 .await?;
         }
 

tests/sqllogictests/suites/base/20+_others/20_00011_max_result_rows

@@ -0,0 +1,38 @@
+statement ok
+DROP DATABASE IF EXISTS db1
+
+statement ok
+CREATE DATABASE db1
+
+statement ok
+USE db1
+
+statement ok
+CREATE TABLE IF NOT EXISTS t1(a INT) Engine = fuse
+
+statement ok
+INSERT INTO t1 (a) values (1), (2), (3)
+
+query I
+SELECT COUNT() FROM (SELECT * FROM t1)
+----
+3
+
+statement ok
+SET max_result_rows=1
+
+query I
+SELECT COUNT() FROM (SELECT * FROM t1)
+----
+1
+
+query I
+SELECT COUNT() FROM (SELECT * FROM t1 limit 2)
+----
+2
+
+statement ok
+DROP TABLE t1
+
+statement ok
+DROP DATABASE db1