feat: show create postgresql foreign table (#5143)

* feat: add show create table for pg in parser

* feat: implement show create table operation

src/datatypes/src/data_type.rs

@@ -370,6 +370,51 @@ impl ConcreteDataType {
             _ => None,
         }
     }
+
+    /// Return the datatype name in postgres type system
+    pub fn postgres_datatype_name(&self) -> &'static str {
+        match self {
+            &ConcreteDataType::Null(_) => "UNKNOWN",
+            &ConcreteDataType::Boolean(_) => "BOOL",
+            &ConcreteDataType::Int8(_) | &ConcreteDataType::UInt8(_) => "CHAR",
+            &ConcreteDataType::Int16(_) | &ConcreteDataType::UInt16(_) => "INT2",
+            &ConcreteDataType::Int32(_) | &ConcreteDataType::UInt32(_) => "INT4",
+            &ConcreteDataType::Int64(_) | &ConcreteDataType::UInt64(_) => "INT8",
+            &ConcreteDataType::Float32(_) => "FLOAT4",
+            &ConcreteDataType::Float64(_) => "FLOAT8",
+            &ConcreteDataType::Binary(_) | &ConcreteDataType::Vector(_) => "BYTEA",
+            &ConcreteDataType::String(_) => "VARCHAR",
+            &ConcreteDataType::Date(_) => "DATE",
+            &ConcreteDataType::DateTime(_) | &ConcreteDataType::Timestamp(_) => "TIMESTAMP",
+            &ConcreteDataType::Time(_) => "TIME",
+            &ConcreteDataType::Interval(_) => "INTERVAL",
+            &ConcreteDataType::Decimal128(_) => "NUMERIC",
+            &ConcreteDataType::Json(_) => "JSON",
+            ConcreteDataType::List(list) => match list.item_type() {
+                &ConcreteDataType::Null(_) => "UNKNOWN",
+                &ConcreteDataType::Boolean(_) => "_BOOL",
+                &ConcreteDataType::Int8(_) | &ConcreteDataType::UInt8(_) => "_CHAR",
+                &ConcreteDataType::Int16(_) | &ConcreteDataType::UInt16(_) => "_INT2",
+                &ConcreteDataType::Int32(_) | &ConcreteDataType::UInt32(_) => "_INT4",
+                &ConcreteDataType::Int64(_) | &ConcreteDataType::UInt64(_) => "_INT8",
+                &ConcreteDataType::Float32(_) => "_FLOAT4",
+                &ConcreteDataType::Float64(_) => "_FLOAT8",
+                &ConcreteDataType::Binary(_) => "_BYTEA",
+                &ConcreteDataType::String(_) => "_VARCHAR",
+                &ConcreteDataType::Date(_) => "_DATE",
+                &ConcreteDataType::DateTime(_) | &ConcreteDataType::Timestamp(_) => "_TIMESTAMP",
+                &ConcreteDataType::Time(_) => "_TIME",
+                &ConcreteDataType::Interval(_) => "_INTERVAL",
+                &ConcreteDataType::Decimal128(_) => "_NUMERIC",
+                &ConcreteDataType::Json(_) => "_JSON",
+                &ConcreteDataType::Duration(_)
+                | &ConcreteDataType::Dictionary(_)
+                | &ConcreteDataType::Vector(_)
+                | &ConcreteDataType::List(_) => "UNKNOWN",
+            },
+            &ConcreteDataType::Duration(_) | &ConcreteDataType::Dictionary(_) => "UNKNOWN",
+        }
+    }
 }
 
 impl From<&ConcreteDataType> for ConcreteDataType {

src/operator/src/statement.rs

@@ -59,6 +59,7 @@ use set::set_query_timeout;
 use snafu::{ensure, OptionExt, ResultExt};
 use sql::statements::copy::{CopyDatabase, CopyDatabaseArgument, CopyTable, CopyTableArgument};
 use sql::statements::set_variables::SetVariables;
+use sql::statements::show::ShowCreateTableVariant;
 use sql::statements::statement::Statement;
 use sql::statements::OptionMap;
 use sql::util::format_raw_object_name;
@@ -317,8 +318,16 @@ impl StatementExecutor {
                     .context(TableNotFoundSnafu { table_name: &table })?;
                 let table_name = TableName::new(catalog, schema, table);
 
-                self.show_create_table(table_name, table_ref, query_ctx)
-                    .await
+                match show.variant {
+                    ShowCreateTableVariant::Original => {
+                        self.show_create_table(table_name, table_ref, query_ctx)
+                            .await
+                    }
+                    ShowCreateTableVariant::PostgresForeignTable => {
+                        self.show_create_table_for_pg(table_name, table_ref, query_ctx)
+                            .await
+                    }
+                }
             }
             Statement::ShowCreateFlow(show) => self.show_create_flow(show, query_ctx).await,
             Statement::ShowCreateView(show) => self.show_create_view(show, query_ctx).await,

src/operator/src/statement/show.rs

@@ -144,6 +144,26 @@ impl StatementExecutor {
             .context(ExecuteStatementSnafu)
     }
 
+    #[tracing::instrument(skip_all)]
+    pub async fn show_create_table_for_pg(
+        &self,
+        table_name: TableName,
+        table: TableRef,
+        query_ctx: QueryContextRef,
+    ) -> Result<Output> {
+        let table_info = table.table_info();
+        if table_info.table_type != TableType::Base {
+            return error::ShowCreateTableBaseOnlySnafu {
+                table_name: table_name.to_string(),
+                table_type: table_info.table_type,
+            }
+            .fail();
+        }
+
+        query::sql::show_create_foreign_table_for_pg(table, query_ctx)
+            .context(ExecuteStatementSnafu)
+    }
+
     #[tracing::instrument(skip_all)]
     pub async fn show_create_view(
         &self,

src/query/src/sql.rs

@@ -45,6 +45,7 @@ use datafusion_expr::{case, col, lit, Expr};
 use datatypes::prelude::*;
 use datatypes::schema::{ColumnDefaultConstraint, ColumnSchema, RawSchema, Schema};
 use datatypes::vectors::StringVector;
+use itertools::Itertools;
 use object_store::ObjectStore;
 use once_cell::sync::Lazy;
 use regex::Regex;
@@ -61,6 +62,7 @@ use sql::statements::show::{
 use sql::statements::statement::Statement;
 use sql::statements::OptionMap;
 use sqlparser::ast::ObjectName;
+use store_api::metric_engine_consts::{is_metric_engine, is_metric_engine_internal_column};
 use table::requests::{FILE_TABLE_LOCATION_KEY, FILE_TABLE_PATTERN_KEY};
 use table::TableRef;
 
@@ -763,6 +765,52 @@ pub fn show_create_table(
     Ok(Output::new_with_record_batches(records))
 }
 
+pub fn show_create_foreign_table_for_pg(
+    table: TableRef,
+    _query_ctx: QueryContextRef,
+) -> Result<Output> {
+    let table_info = table.table_info();
+
+    let table_meta = &table_info.meta;
+    let table_name = &table_info.name;
+    let schema = &table_info.meta.schema;
+    let is_metric_engine = is_metric_engine(&table_meta.engine);
+
+    let columns = schema
+        .column_schemas()
+        .iter()
+        .filter_map(|c| {
+            if is_metric_engine && is_metric_engine_internal_column(&c.name) {
+                None
+            } else {
+                Some(format!(
+                    "\"{}\" {}",
+                    c.name,
+                    c.data_type.postgres_datatype_name()
+                ))
+            }
+        })
+        .join(",\n  ");
+
+    let sql = format!(
+        r#"CREATE FOREIGN TABLE ft_{} (
+  {}
+)
+SERVER greptimedb
+OPTIONS (table_name '{}')"#,
+        table_name, columns, table_name
+    );
+
+    let columns = vec![
+        Arc::new(StringVector::from(vec![table_name.clone()])) as _,
+        Arc::new(StringVector::from(vec![sql])) as _,
+    ];
+    let records = RecordBatches::try_from_columns(SHOW_CREATE_TABLE_OUTPUT_SCHEMA.clone(), columns)
+        .context(error::CreateRecordBatchSnafu)?;
+
+    Ok(Output::new_with_record_batches(records))
+}
+
 pub fn show_create_view(
     view_name: ObjectName,
     definition: &str,

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)]
+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";

tests/cases/standalone/common/show/show_create.result

@@ -46,6 +46,22 @@ SHOW CREATE TABLE system_metrics;
 |                | )                                                         |
 +----------------+-----------------------------------------------------------+
 
+SHOW CREATE TABLE system_metrics FOR POSTGRES_FOREIGN_TABLE;
+
++----------------+------------------------------------------+
+| Table          | Create Table                             |
++----------------+------------------------------------------+
+| system_metrics | CREATE FOREIGN TABLE ft_system_metrics ( |
+|                |   "id" INT4,                             |
+|                |   "host" VARCHAR,                        |
+|                |   "cpu" FLOAT8,                          |
+|                |   "disk" FLOAT4,                         |
+|                |   "ts" TIMESTAMP                         |
+|                | )                                        |
+|                | SERVER greptimedb                        |
+|                | OPTIONS (table_name 'system_metrics')    |
++----------------+------------------------------------------+
+
 DROP TABLE system_metrics;
 
 Affected Rows: 0
@@ -141,6 +157,20 @@ show create table t1;
 |       | )                                 |
 +-------+-----------------------------------+
 
+SHOW CREATE TABLE t1 FOR POSTGRES_FOREIGN_TABLE;
+
++-------+------------------------------+
+| Table | Create Table                 |
++-------+------------------------------+
+| t1    | CREATE FOREIGN TABLE ft_t1 ( |
+|       |   "host" VARCHAR,            |
+|       |   "ts" TIMESTAMP,            |
+|       |   "val" FLOAT8               |
+|       | )                            |
+|       | SERVER greptimedb            |
+|       | OPTIONS (table_name 't1')    |
++-------+------------------------------+
+
 drop table t1;
 
 Affected Rows: 0

tests/cases/standalone/common/show/show_create.sql

@@ -20,6 +20,8 @@ WITH(
 
 SHOW CREATE TABLE system_metrics;
 
+SHOW CREATE TABLE system_metrics FOR POSTGRES_FOREIGN_TABLE;
+
 DROP TABLE system_metrics;
 
 create table table_without_partition (
@@ -57,6 +59,8 @@ show create table phy;
 
 show create table t1;
 
+SHOW CREATE TABLE t1 FOR POSTGRES_FOREIGN_TABLE;
+
 drop table t1;
 
 drop table phy;