Add support for pg_replication_slots (#181)

Add support for pg_replication_slots to the catalog, reducing the number
of failures in the pg_admin startup queries.

Author: mjgarton

datafusion-postgres/src/pg_catalog.rs

@@ -30,6 +30,7 @@ pub mod pg_class;
 pub mod pg_database;
 pub mod pg_get_expr_udf;
 pub mod pg_namespace;
+pub mod pg_replication_slot;
 pub mod pg_settings;
 pub mod pg_tables;
 pub mod pg_views;
@@ -100,6 +101,7 @@ const PG_CATALOG_VIEW_PG_VIEWS: &str = "pg_views";
 const PG_CATALOG_VIEW_PG_MATVIEWS: &str = "pg_matviews";
 const PG_CATALOG_VIEW_PG_TABLES: &str = "pg_tables";
 const PG_CATALOG_VIEW_PG_STAT_USER_TABELS: &str = "pg_stat_user_tables";
+const PG_CATALOG_VIEW_PG_REPLICATION_SLOTS: &str = "pg_replication_slots";
 
 pub const PG_CATALOG_TABLES: &[&str] = &[
     PG_CATALOG_TABLE_PG_AGGREGATE,
@@ -167,6 +169,7 @@ pub const PG_CATALOG_TABLES: &[&str] = &[
     PG_CATALOG_VIEW_PG_VIEWS,
     PG_CATALOG_VIEW_PG_MATVIEWS,
     PG_CATALOG_VIEW_PG_STAT_USER_TABELS,
+    PG_CATALOG_VIEW_PG_REPLICATION_SLOTS,
 ];
 
 #[derive(Debug, Hash, Eq, PartialEq, PartialOrd, Ord)]
@@ -352,7 +355,10 @@ impl<C: CatalogInfo> SchemaProvider for PgCatalogSchemaProvider<C> {
             PG_CATALOG_VIEW_PG_STAT_USER_TABELS => {
                 Ok(Some(Arc::new(pg_views::pg_stat_user_tables()?)))
             }
-
+            PG_CATALOG_VIEW_PG_REPLICATION_SLOTS => {
+                let table = pg_replication_slot::pg_replication_slots()?;
+                Ok(Some(table))
+            }
             _ => Ok(None),
         }
     }

datafusion-postgres/src/pg_catalog/pg_replication_slot.rs

@@ -0,0 +1,30 @@
+use crate::pg_catalog::empty_table::EmptyTable;
+use datafusion::arrow::datatypes::{DataType, Field, Schema};
+use datafusion::catalog::TableProvider;
+use datafusion::error::Result;
+use std::sync::Arc;
+
+pub(crate) fn pg_replication_slots() -> Result<Arc<dyn TableProvider>> {
+    let schema = Arc::new(Schema::new(vec![
+        Field::new("slot_name", DataType::Utf8, true),
+        Field::new("plugin", DataType::Utf8, true),
+        Field::new("slot_type", DataType::Utf8, true),
+        Field::new("datoid", DataType::Int32, true),
+        Field::new("database", DataType::Utf8, true),
+        Field::new("temporary", DataType::Boolean, false),
+        Field::new("active", DataType::Boolean, false),
+        Field::new("active_pid", DataType::Int32, true),
+        Field::new("xmin", DataType::Int32, true),
+        Field::new("catalog_xmin", DataType::Int32, true),
+        Field::new("restart_lsn", DataType::Utf8, true), // TODO: is this the correct type to use?
+        Field::new("confirmed_flush_lsn", DataType::Utf8, true), // TODO: is this the correct type to use?
+        Field::new("wal_status", DataType::Utf8, true),
+        Field::new("safe_wal_size", DataType::Int64, true),
+        Field::new("two_phase", DataType::Boolean, false),
+        Field::new("conflicting", DataType::Boolean, false),
+    ]));
+
+    let table = EmptyTable::new(schema).try_into_memtable()?;
+
+    Ok(Arc::new(table))
+}