Merge pull request #2 from MaterializeInc/show-columns

Support `SHOW COLUMNS FROM mytable`

Author: quodlibetor

src/ast/mod.rs

@@ -450,6 +450,13 @@ pub enum Statement {
     Peek { name: ObjectName },
     /// TAIL
     Tail { name: ObjectName },
+    /// The mysql-ish `SHOW COLUMNS FROM`
+    ///
+    /// ```sql
+    /// SHOW COLUMNS FROM mydb.mytable;
+    /// ```
+    /// Limitations: doesn't support `LIKE`,  `WHERE` or `SHOW COLUMNS FROM mytable FROM mydb;`
+    ShowColumns { table_name: ObjectName },
 }
 
 impl fmt::Display for Statement {
@@ -655,6 +662,7 @@ impl fmt::Display for Statement {
                 write!(f, "ROLLBACK{}", if *chain { " AND CHAIN" } else { "" },)
             }
             Statement::Peek { name } => write!(f, "PEEK {}", name),
+            Statement::ShowColumns { table_name } => write!(f, "SHOW COLUMNS FROM {}", table_name),
             Statement::Tail { name } => write!(f, "TAIL {}", name),
         }
     }

src/ast/visit.rs

@@ -465,6 +465,10 @@ pub trait Visit<'ast> {
         visit_peek(self, name)
     }
 
+    fn visit_show_columns(&mut self, name: &'ast ObjectName) {
+        visit_show_columns(self, name)
+    }
+
     fn visit_tail(&mut self, name: &'ast ObjectName) {
         visit_tail(self, name)
     }
@@ -542,6 +546,7 @@ pub fn visit_statement<'ast, V: Visit<'ast> + ?Sized>(visitor: &mut V, statement
         Statement::Peek { name } => {
             visitor.visit_peek(name);
         }
+        Statement::ShowColumns { table_name } => visitor.visit_show_columns(table_name),
         Statement::Tail { name } => {
             visitor.visit_tail(name);
         }
@@ -1366,6 +1371,10 @@ pub fn visit_peek<'ast, V: Visit<'ast> + ?Sized>(visitor: &mut V, name: &'ast Ob
     visitor.visit_object_name(name);
 }
 
+pub fn visit_show_columns<'ast, V: Visit<'ast> + ?Sized>(visitor: &mut V, name: &'ast ObjectName) {
+    visitor.visit_object_name(name);
+}
+
 pub fn visit_tail<'ast, V: Visit<'ast> + ?Sized>(visitor: &mut V, name: &'ast ObjectName) {
     visitor.visit_object_name(name);
 }

src/dialect/keywords.rs

@@ -102,6 +102,7 @@ define_keywords!(
     COLLATE,
     COLLECT,
     COLUMN,
+    COLUMNS,
     COMMIT,
     COMMITTED,
     CONDITION,
@@ -337,6 +338,7 @@ define_keywords!(
     SERIALIZABLE,
     SESSION_USER,
     SET,
+    SHOW,
     SIMILAR,
     SINK,
     SMALLINT,

src/parser.rs

@@ -137,6 +137,7 @@ impl Parser {
                     "PEEK" => Ok(Statement::Peek {
                         name: self.parse_object_name()?,
                     }),
+                    "SHOW" => Ok(self.parse_show()?),
                     "TAIL" => Ok(Statement::Tail {
                         name: self.parse_object_name()?,
                     }),
@@ -1663,6 +1664,25 @@ impl Parser {
         })
     }
 
+    pub fn parse_show(&mut self) -> Result<Statement, ParserError> {
+        if self.parse_keyword("COLUMNS") {
+            self.parse_show_columns()
+        } else {
+            self.expected("COLUMNS", self.peek_token())
+        }
+    }
+
+    fn parse_show_columns(&mut self) -> Result<Statement, ParserError> {
+        if !self.parse_keyword("FROM") {
+            return self.expected("FROM", self.peek_token());
+        }
+        let table_or_schema = self.parse_object_name()?;
+
+        Ok(Statement::ShowColumns {
+            table_name: table_or_schema,
+        })
+    }
+
     pub fn parse_table_and_joins(&mut self) -> Result<TableWithJoins, ParserError> {
         let relation = self.parse_table_factor()?;
 

tests/sqlparser_common.rs

@@ -1459,6 +1459,28 @@ fn parse_searched_case_expr() {
     );
 }
 
+#[test]
+fn parse_show_columns() {
+    assert_eq!(
+        verified_stmt("SHOW COLUMNS FROM mytable"),
+        Statement::ShowColumns {
+            table_name: ObjectName(vec!["mytable".to_string()])
+        }
+    );
+    assert_eq!(
+        verified_stmt("SHOW COLUMNS FROM mydb.mytable"),
+        Statement::ShowColumns {
+            table_name: ObjectName(vec!["mydb".to_string(), "mytable".to_string()])
+        }
+    );
+
+    // unhandled things are truly unhandled
+    match parse_sql_statements("SHOW COLUMNS FROM mytable FROM mydb") {
+        Err(_) => {}
+        Ok(val) => panic!("unexpected successful parse: {:?}", val),
+    }
+}
+
 #[test]
 fn parse_simple_case_expr() {
     // ANSI calls a CASE expression with an operand "<simple case>"