functions: Add lower support

common/functions/Cargo.toml

@@ -38,6 +38,7 @@ hex = "0.4.3"
 base64 = "0.13.0"
 itertools = "0.10.3"
 num-format = "0.4"
+bstr = "0.2.17"
 
 [dev-dependencies]
 bumpalo = "3.8.0"

common/functions/src/scalars/strings/lower.rs

@@ -0,0 +1,32 @@
+// 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 bstr::ByteSlice;
+
+use super::string2string::String2StringFunction;
+use super::string2string::StringOperator;
+
+#[derive(Clone, Default)]
+pub struct Lower;
+
+impl StringOperator for Lower {
+    #[inline]
+    fn apply_with_no_null<'a>(&'a mut self, s: &'a [u8], buffer: &mut [u8]) -> usize {
+        buffer.copy_from_slice(&s.to_lowercase());
+
+        s.len()
+    }
+}
+
+pub type LowerFunction = String2StringFunction<Lower>;

common/functions/src/scalars/strings/mod.rs

@@ -29,6 +29,7 @@ mod insert;
 mod leftright;
 mod length;
 mod locate;
+mod lower;
 mod oct;
 mod octet_length;
 mod ord;
@@ -67,6 +68,7 @@ pub use length::LengthFunction;
 pub use locate::InstrFunction;
 pub use locate::LocateFunction;
 pub use locate::PositionFunction;
+pub use lower::LowerFunction;
 pub use oct::OctFunction;
 pub use octet_length::OctetLengthFunction;
 pub use ord::OrdFunction;

common/functions/src/scalars/strings/string.rs

@@ -34,6 +34,7 @@ use crate::scalars::LeftFunction;
 use crate::scalars::LeftPadFunction;
 use crate::scalars::LengthFunction;
 use crate::scalars::LocateFunction;
+use crate::scalars::LowerFunction;
 use crate::scalars::OctFunction;
 use crate::scalars::OctetLengthFunction;
 use crate::scalars::OrdFunction;
@@ -98,5 +99,7 @@ impl StringFunction {
         factory.register("find_in_set", FindInSetFunction::desc());
         factory.register("length", LengthFunction::desc());
         factory.register("format", FormatFunction::desc());
+        factory.register("lower", LowerFunction::desc());
+        factory.register("lcase", LowerFunction::desc());
     }
 }

common/functions/tests/it/scalars/strings/lower.rs

@@ -0,0 +1,74 @@
+// 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 common_datavalues::prelude::*;
+use common_exception::Result;
+use common_functions::scalars::LowerFunction;
+
+use super::run_tests;
+use super::Test;
+
+#[test]
+fn test_lower_function() -> Result<()> {
+    let schema = DataSchemaRefExt::create(vec![DataField::new("a", DataType::String, false)]);
+
+    let tests = vec![
+        Test {
+            name: "lower-abc-passed",
+            display: "lower",
+            nullable: true,
+            arg_names: vec!["a"],
+            columns: vec![Series::new(vec!["Abc"]).into()],
+            func: LowerFunction::try_create("lower")?,
+            expect: DataColumn::Constant(DataValue::String(Some("abc".as_bytes().to_vec())), 1),
+            error: "",
+        },
+        Test {
+            name: "lower-utf8-passed",
+            display: "lower",
+            nullable: true,
+            arg_names: vec!["a"],
+            columns: vec![Series::new(vec!["Dobrý den"]).into()],
+            func: LowerFunction::try_create("lower")?,
+            expect: DataColumn::Constant(
+                DataValue::String(Some("dobrý den".as_bytes().to_vec())),
+                1,
+            ),
+            error: "",
+        },
+        Test {
+            name: "lcase-utf8-passed",
+            display: "lcase",
+            nullable: true,
+            arg_names: vec!["a"],
+            columns: vec![Series::new(vec!["Dobrý den"]).into()],
+            func: LowerFunction::try_create("lcase")?,
+            expect: DataColumn::Constant(
+                DataValue::String(Some("dobrý den".as_bytes().to_vec())),
+                1,
+            ),
+            error: "",
+        },
+        Test {
+            name: "lcase-null-passed",
+            display: "lcase",
+            nullable: true,
+            arg_names: vec!["a"],
+            columns: vec![Series::new(vec![Option::<Vec<u8>>::None]).into()],
+            func: LowerFunction::try_create("lcase")?,
+            expect: DataColumn::Constant(DataValue::String(None), 1),
+            error: "",
+        },
+    ];
+    run_tests(tests, schema)
+}

common/functions/tests/it/scalars/strings/mod.rs

@@ -13,8 +13,10 @@
 // limitations under the License.
 
 mod locate;
+mod lower;
 mod substring;
 mod trim;
 
 mod utils;
+
 pub use utils::*;

tests/suites/0_stateless/02_0042_function_strings_lower.result

@@ -0,0 +1,3 @@
+hello,world!
+здравствуйте
+NULL

tests/suites/0_stateless/02_0042_function_strings_lower.sql

@@ -0,0 +1,3 @@
+SELECT LOWER('Hello,World!');
+SELECT LOWER('Здравствуйте');
+SELECT LOWER(NULL);

website/databend/docs/user/sqlstatement/string-functions/lcase.md

@@ -0,0 +1,11 @@
+---
+title: LCASE
+---
+
+Synonym for LOWER(str).
+
+## Syntax
+
+```sql
+LCASE(str);
+```

website/databend/docs/user/sqlstatement/string-functions/lower.md

@@ -0,0 +1,33 @@
+---
+title: LOWER
+---
+
+Returns the string str with all characters changed to lowercase.
+
+## Syntax
+
+```sql
+LOWER(str);
+```
+
+## Arguments
+
+| Arguments | Description                |
+|-----------|----------------------------|
+| str       | The string to be lowercase |
+
+
+## Return Type
+
+A string data type value.
+
+## Examples
+
+```txt
+SELECT LOWER('Hello, World!')
++----------------------------+
+| substring('Hello, World!') |
++----------------------------+
+| hello, world!              |
++----------------------------+
+```