feat: show create postgresql foreign table (#5143)

* feat: add show create table for pg in parser

* feat: implement show create table operation

* fix: adopt upstream changes

src/sql/src/parsers/show_parser.rs

@@ -21,9 +21,9 @@ use crate::error::{
 };
 use crate::parser::ParserContext;
 use crate::statements::show::{
-    ShowColumns, ShowCreateDatabase, ShowCreateFlow, ShowCreateTable, ShowCreateView,
-    ShowDatabases, ShowFlows, ShowIndex, ShowKind, ShowStatus, ShowTableStatus, ShowTables,
-    ShowVariables, ShowViews,
+    ShowColumns, ShowCreateDatabase, ShowCreateFlow, ShowCreateTable, ShowCreateTableVariant,
+    ShowCreateView, ShowDatabases, ShowFlows, ShowIndex, ShowKind, ShowStatus, ShowTableStatus,
+    ShowTables, ShowVariables, ShowViews,
 };
 use crate::statements::statement::Statement;
 
@@ -146,7 +146,19 @@ impl ParserContext<'_> {
                 name: table_name.to_string(),
             }
         );
-        Ok(Statement::ShowCreateTable(ShowCreateTable { table_name }))
+        let mut variant = ShowCreateTableVariant::Original;
+        if self.consume_token("FOR") {
+            if self.consume_token("POSTGRES_FOREIGN_TABLE") {
+                variant = ShowCreateTableVariant::PostgresForeignTable;
+            } else {
+                self.unsupported(self.peek_token_as_string())?;
+            }
+        }
+
+        Ok(Statement::ShowCreateTable(ShowCreateTable {
+            table_name,
+            variant,
+        }))
     }
 
     fn parse_show_create_flow(&mut self) -> Result<Statement> {

src/sql/src/statements/show.rs

@@ -179,12 +179,26 @@ impl Display for ShowCreateDatabase {
 #[derive(Debug, Clone, PartialEq, Eq, Visit, VisitMut, Serialize)]
 pub struct ShowCreateTable {
     pub table_name: ObjectName,
+    pub variant: ShowCreateTableVariant,
+}
+
+/// Variant of a show create table
+#[derive(Default, Debug, Clone, PartialEq, Eq, Visit, VisitMut, Serialize)]
+pub enum ShowCreateTableVariant {
+    #[default]
+    Original,
+    PostgresForeignTable,
 }
 
 impl Display for ShowCreateTable {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let table_name = &self.table_name;
-        write!(f, r#"SHOW CREATE TABLE {table_name}"#)
+        write!(f, r#"SHOW CREATE TABLE {table_name}"#)?;
+        if let ShowCreateTableVariant::PostgresForeignTable = self.variant {
+            write!(f, " FOR POSTGRES_FOREIGN_TABLE")?;
+        }
+
+        Ok(())
     }
 }
 
@@ -344,12 +358,31 @@ mod tests {
             Statement::ShowCreateTable(show) => {
                 let table_name = show.table_name.to_string();
                 assert_eq!(table_name, "test");
+                assert_eq!(show.variant, ShowCreateTableVariant::Original);
+            }
+            _ => {
+                unreachable!();
+            }
+        }
+
+        let sql = "SHOW CREATE TABLE test FOR POSTGRES_FOREIGN_TABLE";
+        let stmts: Vec<Statement> =
+            ParserContext::create_with_dialect(sql, &GreptimeDbDialect {}, ParseOptions::default())
+                .unwrap();
+        assert_eq!(1, stmts.len());
+        assert_matches!(&stmts[0], Statement::ShowCreateTable { .. });
+        match &stmts[0] {
+            Statement::ShowCreateTable(show) => {
+                let table_name = show.table_name.to_string();
+                assert_eq!(table_name, "test");
+                assert_eq!(show.variant, ShowCreateTableVariant::PostgresForeignTable);
             }
             _ => {
                 unreachable!();
             }
         }
     }
+
     #[test]
     pub fn test_show_create_missing_table_name() {
         let sql = "SHOW CREATE TABLE";
@@ -361,6 +394,17 @@ mod tests {
         .is_err());
     }
 
+    #[test]
+    pub fn test_show_create_unknown_for() {
+        let sql = "SHOW CREATE TABLE t FOR UNKNOWN";
+        assert!(ParserContext::create_with_dialect(
+            sql,
+            &GreptimeDbDialect {},
+            ParseOptions::default()
+        )
+        .is_err());
+    }
+
     #[test]
     pub fn test_show_create_flow() {
         let sql = "SHOW CREATE FLOW test";