feat: support show views statement (#4360)

This commit enables show view statement which will display a list of views
names.

src/sql/src/parsers/show_parser.rs

@@ -22,7 +22,7 @@ use crate::error::{
 use crate::parser::ParserContext;
 use crate::statements::show::{
     ShowColumns, ShowCreateFlow, ShowCreateTable, ShowCreateView, ShowDatabases, ShowIndex,
-    ShowKind, ShowStatus, ShowTableStatus, ShowTables, ShowVariables,
+    ShowKind, ShowStatus, ShowTableStatus, ShowTables, ShowVariables, ShowViews,
 };
 use crate::statements::statement::Statement;
 
@@ -44,6 +44,8 @@ impl<'a> ParserContext<'a> {
             } else {
                 self.unsupported(self.peek_token_as_string())
             }
+        } else if self.consume_token("VIEWS") {
+            self.parse_show_views()
         } else if self.matches_keyword(Keyword::CHARSET) {
             self.parser.next_token();
             Ok(Statement::ShowCharset(self.parse_show_kind()?))
@@ -430,6 +432,28 @@ impl<'a> ParserContext<'a> {
             _ => self.unsupported(self.peek_token_as_string()),
         }
     }
+
+    fn parse_show_views(&mut self) -> Result<Statement> {
+        let database = match self.parser.peek_token().token {
+            Token::EOF | Token::SemiColon => {
+                return Ok(Statement::ShowViews(ShowViews {
+                    kind: ShowKind::All,
+                    database: None,
+                }));
+            }
+
+            // SHOW VIEWS [in | FROM] [DATABASE]
+            Token::Word(w) => match w.keyword {
+                Keyword::IN | Keyword::FROM => self.parse_db_name()?,
+                _ => None,
+            },
+            _ => None,
+        };
+
+        let kind = self.parse_show_kind()?;
+
+        Ok(Statement::ShowViews(ShowViews { kind, database }))
+    }
 }
 
 #[cfg(test)]
@@ -942,4 +966,38 @@ mod tests {
         );
         assert_eq!(sql, stmts[0].to_string());
     }
+
+    #[test]
+    pub fn test_show_views() {
+        let sql = "SHOW VIEWS";
+        let result =
+            ParserContext::create_with_dialect(sql, &GreptimeDbDialect {}, ParseOptions::default());
+        let stmts = result.unwrap();
+        assert_eq!(1, stmts.len());
+        assert_eq!(
+            stmts[0],
+            Statement::ShowViews(ShowViews {
+                kind: ShowKind::All,
+                database: None,
+            })
+        );
+        assert_eq!(sql, stmts[0].to_string());
+    }
+
+    #[test]
+    pub fn test_show_views_in_db() {
+        let sql = "SHOW VIEWS IN d1";
+        let result =
+            ParserContext::create_with_dialect(sql, &GreptimeDbDialect {}, ParseOptions::default());
+        let stmts = result.unwrap();
+        assert_eq!(1, stmts.len());
+        assert_eq!(
+            stmts[0],
+            Statement::ShowViews(ShowViews {
+                kind: ShowKind::All,
+                database: Some("d1".to_string()),
+            })
+        );
+        assert_eq!(sql, stmts[0].to_string());
+    }
 }

src/sql/src/statements/show.rs

@@ -200,6 +200,25 @@ impl Display for ShowCreateView {
     }
 }
 
+/// SQL structure for `SHOW VIEWS`.
+#[derive(Debug, Clone, PartialEq, Eq, Visit, VisitMut)]
+pub struct ShowViews {
+    pub kind: ShowKind,
+    pub database: Option<String>,
+}
+
+impl Display for ShowViews {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "SHOW VIEWS")?;
+        if let Some(database) = &self.database {
+            write!(f, " IN {database}")?;
+        }
+        format_kind!(self, f);
+
+        Ok(())
+    }
+}
+
 /// SQL structure for `SHOW VARIABLES xxx`.
 #[derive(Debug, Clone, PartialEq, Eq, Visit, VisitMut)]
 pub struct ShowVariables {
@@ -473,6 +492,49 @@ SHOW FULL TABLES"#,
         }
     }
 
+    #[test]
+    fn test_display_show_views() {
+        let sql = r"show views in d1;";
+        let stmts: Vec<Statement> =
+            ParserContext::create_with_dialect(sql, &GreptimeDbDialect {}, ParseOptions::default())
+                .unwrap();
+        assert_eq!(1, stmts.len());
+        assert_matches!(&stmts[0], Statement::ShowViews { .. });
+        match &stmts[0] {
+            Statement::ShowViews(show) => {
+                let new_sql = format!("\n{}", show);
+                assert_eq!(
+                    r#"
+SHOW VIEWS IN d1"#,
+                    &new_sql
+                );
+            }
+            _ => {
+                unreachable!();
+            }
+        }
+
+        let sql = r"show views;";
+        let stmts: Vec<Statement> =
+            ParserContext::create_with_dialect(sql, &GreptimeDbDialect {}, ParseOptions::default())
+                .unwrap();
+        assert_eq!(1, stmts.len());
+        assert_matches!(&stmts[0], Statement::ShowViews { .. });
+        match &stmts[0] {
+            Statement::ShowViews(show) => {
+                let new_sql = format!("\n{}", show);
+                assert_eq!(
+                    r#"
+SHOW VIEWS"#,
+                    &new_sql
+                );
+            }
+            _ => {
+                unreachable!();
+            }
+        }
+    }
+
     #[test]
     fn test_display_show_databases() {
         let sql = r"show databases;";

src/sql/src/statements/statement.rs

@@ -32,7 +32,7 @@ use crate::statements::query::Query;
 use crate::statements::set_variables::SetVariables;
 use crate::statements::show::{
     ShowColumns, ShowCreateFlow, ShowCreateTable, ShowCreateView, ShowDatabases, ShowIndex,
-    ShowKind, ShowStatus, ShowTableStatus, ShowTables, ShowVariables,
+    ShowKind, ShowStatus, ShowTableStatus, ShowTables, ShowVariables, ShowViews,
 };
 use crate::statements::tql::Tql;
 use crate::statements::truncate::TruncateTable;
@@ -91,6 +91,8 @@ pub enum Statement {
     ShowCreateView(ShowCreateView),
     // SHOW STATUS
     ShowStatus(ShowStatus),
+    // SHOW VIEWS
+    ShowViews(ShowViews),
     // DESCRIBE TABLE
     DescribeTable(DescribeTable),
     // EXPLAIN QUERY
@@ -132,6 +134,7 @@ impl Display for Statement {
             Statement::ShowCreateTable(s) => s.fmt(f),
             Statement::ShowCreateFlow(s) => s.fmt(f),
             Statement::ShowCreateView(s) => s.fmt(f),
+            Statement::ShowViews(s) => s.fmt(f),
             Statement::ShowStatus(s) => s.fmt(f),
             Statement::DescribeTable(s) => s.fmt(f),
             Statement::Explain(s) => s.fmt(f),