Support MySQL SHOW COLUMNS statement

Co-authored-by: Nikhil Benesch <nikhil.benesch@gmail.com>

tests/sqlparser_mysql.rs

@@ -0,0 +1,110 @@
+// 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.
+
+#![warn(clippy::all)]
+
+//! Test SQL syntax specific to MySQL. The parser based on the generic dialect
+//! is also tested (on the inputs it can handle).
+
+use sqlparser::ast::*;
+use sqlparser::dialect::{GenericDialect, MySqlDialect};
+use sqlparser::test_utils::*;
+
+#[test]
+fn parse_identifiers() {
+    mysql().verified_stmt("SELECT $a$, àà");
+}
+
+#[test]
+fn parse_show_columns() {
+    let table_name = ObjectName(vec!["mytable".to_string()]);
+    assert_eq!(
+        mysql_and_generic().verified_stmt("SHOW COLUMNS FROM mytable"),
+        Statement::ShowColumns {
+            extended: false,
+            full: false,
+            table_name: table_name.clone(),
+            filter: None,
+        }
+    );
+    assert_eq!(
+        mysql_and_generic().verified_stmt("SHOW COLUMNS FROM mydb.mytable"),
+        Statement::ShowColumns {
+            extended: false,
+            full: false,
+            table_name: ObjectName(vec!["mydb".to_string(), "mytable".to_string()]),
+            filter: None,
+        }
+    );
+    assert_eq!(
+        mysql_and_generic().verified_stmt("SHOW EXTENDED COLUMNS FROM mytable"),
+        Statement::ShowColumns {
+            extended: true,
+            full: false,
+            table_name: table_name.clone(),
+            filter: None,
+        }
+    );
+    assert_eq!(
+        mysql_and_generic().verified_stmt("SHOW FULL COLUMNS FROM mytable"),
+        Statement::ShowColumns {
+            extended: false,
+            full: true,
+            table_name: table_name.clone(),
+            filter: None,
+        }
+    );
+    assert_eq!(
+        mysql_and_generic().verified_stmt("SHOW COLUMNS FROM mytable LIKE 'pattern'"),
+        Statement::ShowColumns {
+            extended: false,
+            full: false,
+            table_name: table_name.clone(),
+            filter: Some(ShowStatementFilter::Like("pattern".into())),
+        }
+    );
+    assert_eq!(
+        mysql_and_generic().verified_stmt("SHOW COLUMNS FROM mytable WHERE 1 = 2"),
+        Statement::ShowColumns {
+            extended: false,
+            full: false,
+            table_name: table_name.clone(),
+            filter: Some(ShowStatementFilter::Where(
+                mysql_and_generic().verified_expr("1 = 2")
+            )),
+        }
+    );
+    mysql_and_generic()
+        .one_statement_parses_to("SHOW FIELDS FROM mytable", "SHOW COLUMNS FROM mytable");
+    mysql_and_generic()
+        .one_statement_parses_to("SHOW COLUMNS IN mytable", "SHOW COLUMNS FROM mytable");
+    mysql_and_generic()
+        .one_statement_parses_to("SHOW FIELDS IN mytable", "SHOW COLUMNS FROM mytable");
+
+    // unhandled things are truly unhandled
+    match mysql_and_generic().parse_sql_statements("SHOW COLUMNS FROM mytable FROM mydb") {
+        Err(_) => {}
+        Ok(val) => panic!("unexpected successful parse: {:?}", val),
+    }
+}
+
+fn mysql() -> TestedDialects {
+    TestedDialects {
+        dialects: vec![Box::new(MySqlDialect {})],
+    }
+}
+
+fn mysql_and_generic() -> TestedDialects {
+    TestedDialects {
+        dialects: vec![Box::new(MySqlDialect {}), Box::new(GenericDialect {})],
+    }
+}