feat: Allow sql parser to parse show-create-table statement (#347)

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

* feat: Add ShowCreateTable to Statement

src/datanode/src/instance/sql.rs

@@ -77,6 +77,9 @@ impl Instance {
             Statement::ShowTables(stmt) => {
                 self.sql_handler.execute(SqlRequest::ShowTables(stmt)).await
             }
+            Statement::ShowCreateTable(_stmt) => {
+                unimplemented!("SHOW CREATE TABLE is unimplemented yet");
+            }
         }
     }
 }

src/query/src/datafusion/planner.rs

@@ -48,6 +48,7 @@ where
             Statement::Query(qb) => self.query_to_plan(qb),
             Statement::ShowTables(_)
             | Statement::ShowDatabases(_)
+            | Statement::ShowCreateTable(_)
             | Statement::Create(_)
             | Statement::Alter(_)
             | Statement::Insert(_) => unreachable!(),

src/sql/src/error.rs

@@ -83,6 +83,9 @@ pub enum Error {
     #[snafu(display("Invalid database name: {}", name))]
     InvalidDatabaseName { name: String, backtrace: Backtrace },
 
+    #[snafu(display("Invalid table name: {}", name))]
+    InvalidTableName { name: String, backtrace: Backtrace },
+
     #[snafu(display("Invalid default constraint, column: {}, source: {}", column, source))]
     InvalidDefault {
         column: String,
@@ -106,7 +109,9 @@ impl ErrorExt for Error {
             | SqlTypeNotSupported { .. }
             | InvalidDefault { .. } => StatusCode::InvalidSyntax,
 
-            InvalidDatabaseName { .. } | ColumnTypeMismatch { .. } => StatusCode::InvalidArguments,
+            InvalidDatabaseName { .. } | ColumnTypeMismatch { .. } | InvalidTableName { .. } => {
+                StatusCode::InvalidArguments
+            }
         }
     }
 

src/sql/src/parser.rs

@@ -5,8 +5,10 @@ use sqlparser::parser::Parser;
 use sqlparser::parser::ParserError;
 use sqlparser::tokenizer::{Token, Tokenizer};
 
-use crate::error::{self, InvalidDatabaseNameSnafu, Result, SyntaxSnafu, TokenizerSnafu};
-use crate::statements::show::{ShowDatabases, ShowKind, ShowTables};
+use crate::error::{
+    self, InvalidDatabaseNameSnafu, InvalidTableNameSnafu, Result, SyntaxSnafu, TokenizerSnafu,
+};
+use crate::statements::show::{ShowCreateTable, ShowDatabases, ShowKind, ShowTables};
 use crate::statements::statement::Statement;
 
 /// GrepTime SQL parser context, a simple wrapper for Datafusion SQL parser.
@@ -102,11 +104,38 @@ impl<'a> ParserContext<'a> {
         } else if self.matches_keyword(Keyword::TABLES) {
             self.parser.next_token();
             self.parse_show_tables()
+        } else if self.consume_token("CREATE") {
+            if self.consume_token("TABLE") {
+                self.parse_show_create_table()
+            } else {
+                self.unsupported(self.peek_token_as_string())
+            }
         } else {
             self.unsupported(self.peek_token_as_string())
         }
     }
 
+    /// Parse SHOW CREATE TABLE statement
+    fn parse_show_create_table(&mut self) -> Result<Statement> {
+        let table_name =
+            self.parser
+                .parse_object_name()
+                .with_context(|_| error::UnexpectedSnafu {
+                    sql: self.sql,
+                    expected: "a table name",
+                    actual: self.peek_token_as_string(),
+                })?;
+        ensure!(
+            !table_name.0.is_empty(),
+            InvalidTableNameSnafu {
+                name: table_name.to_string(),
+            }
+        );
+        Ok(Statement::ShowCreateTable(ShowCreateTable {
+            table_name: table_name.to_string(),
+        }))
+    }
+
     fn parse_show_tables(&mut self) -> Result<Statement> {
         let database = match self.parser.peek_token() {
             Token::EOF | Token::SemiColon => {

src/sql/src/statements/show.rs

@@ -40,6 +40,12 @@ pub struct ShowTables {
     pub database: Option<String>,
 }
 
+/// SQL structure for `SHOW CREATE TABLE`.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ShowCreateTable {
+    pub table_name: String,
+}
+
 #[cfg(test)]
 mod tests {
     use std::assert_matches::assert_matches;
@@ -94,4 +100,27 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    pub fn test_show_create_table() {
+        let sql = "SHOW CREATE TABLE test";
+        let stmts: Vec<Statement> =
+            ParserContext::create_with_dialect(sql, &GenericDialect {}).unwrap();
+        assert_eq!(1, stmts.len());
+        assert_matches!(&stmts[0], Statement::ShowCreateTable { .. });
+        match &stmts[0] {
+            Statement::ShowCreateTable(show) => {
+                let table_name = show.table_name.as_str();
+                assert_eq!(table_name, "test");
+            }
+            _ => {
+                unreachable!();
+            }
+        }
+    }
+    #[test]
+    pub fn test_show_create_missing_table_name() {
+        let sql = "SHOW CREATE TABLE";
+        ParserContext::create_with_dialect(sql, &GenericDialect {}).unwrap_err();
+    }
 }

src/sql/src/statements/statement.rs

@@ -5,7 +5,7 @@ use crate::statements::alter::AlterTable;
 use crate::statements::create_table::CreateTable;
 use crate::statements::insert::Insert;
 use crate::statements::query::Query;
-use crate::statements::show::{ShowDatabases, ShowTables};
+use crate::statements::show::{ShowCreateTable, ShowDatabases, ShowTables};
 
 /// Tokens parsed by `DFParser` are converted into these values.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -22,6 +22,8 @@ pub enum Statement {
     ShowDatabases(ShowDatabases),
     // SHOW TABLES
     ShowTables(ShowTables),
+    // SHOW CREATE TABLE
+    ShowCreateTable(ShowCreateTable),
 }
 
 /// Converts Statement to sqlparser statement
@@ -36,6 +38,9 @@ impl TryFrom<Statement> for SpStatement {
             Statement::ShowTables(_) => Err(ParserError::ParserError(
                 "sqlparser does not support SHOW TABLES query.".to_string(),
             )),
+            Statement::ShowCreateTable(_) => Err(ParserError::ParserError(
+                "sqlparser does not support SHOW CREATE TABLE query.".to_string(),
+            )),
             Statement::Query(s) => Ok(SpStatement::Query(Box::new(s.inner))),
             Statement::Insert(i) => Ok(i.inner),
             Statement::Create(_) | Statement::Alter(_) => unimplemented!(),