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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
//! Describes the interface and built-in implementations of catalogs,
//! representing collections of named schemas.
use crate::catalog::schema::SchemaProvider;
use dashmap::DashMap;
use datafusion_common::{DataFusionError, Result};
use std::any::Any;
use std::sync::Arc;
/// Represent a list of named catalogs
pub trait CatalogList: Sync + Send {
/// Returns the catalog list as [`Any`](std::any::Any)
/// so that it can be downcast to a specific implementation.
fn as_any(&self) -> &dyn Any;
/// Adds a new catalog to this catalog list
/// If a catalog of the same name existed before, it is replaced in the list and returned.
fn register_catalog(
&self,
name: String,
catalog: Arc<dyn CatalogProvider>,
) -> Option<Arc<dyn CatalogProvider>>;
/// Retrieves the list of available catalog names
fn catalog_names(&self) -> Vec<String>;
/// Retrieves a specific catalog by name, provided it exists.
fn catalog(&self, name: &str) -> Option<Arc<dyn CatalogProvider>>;
}
/// Simple in-memory list of catalogs
pub struct MemoryCatalogList {
/// Collection of catalogs containing schemas and ultimately TableProviders
pub catalogs: DashMap<String, Arc<dyn CatalogProvider>>,
}
impl MemoryCatalogList {
/// Instantiates a new `MemoryCatalogList` with an empty collection of catalogs
pub fn new() -> Self {
Self {
catalogs: DashMap::new(),
}
}
}
impl Default for MemoryCatalogList {
fn default() -> Self {
Self::new()
}
}
impl CatalogList for MemoryCatalogList {
fn as_any(&self) -> &dyn Any {
self
}
fn register_catalog(
&self,
name: String,
catalog: Arc<dyn CatalogProvider>,
) -> Option<Arc<dyn CatalogProvider>> {
self.catalogs.insert(name, catalog)
}
fn catalog_names(&self) -> Vec<String> {
self.catalogs.iter().map(|c| c.key().clone()).collect()
}
fn catalog(&self, name: &str) -> Option<Arc<dyn CatalogProvider>> {
self.catalogs.get(name).map(|c| c.value().clone())
}
}
impl Default for MemoryCatalogProvider {
fn default() -> Self {
Self::new()
}
}
/// Represents a catalog, comprising a number of named schemas.
pub trait CatalogProvider: Sync + Send {
/// Returns the catalog provider as [`Any`](std::any::Any)
/// so that it can be downcast to a specific implementation.
fn as_any(&self) -> &dyn Any;
/// Retrieves the list of available schema names in this catalog.
fn schema_names(&self) -> Vec<String>;
/// Retrieves a specific schema from the catalog by name, provided it exists.
fn schema(&self, name: &str) -> Option<Arc<dyn SchemaProvider>>;
/// Adds a new schema to this catalog.
///
/// If a schema of the same name existed before, it is replaced in
/// the catalog and returned.
///
/// By default returns a "Not Implemented" error
fn register_schema(
&self,
name: &str,
schema: Arc<dyn SchemaProvider>,
) -> Result<Option<Arc<dyn SchemaProvider>>> {
// use variables to avoid unused variable warnings
let _ = name;
let _ = schema;
Err(DataFusionError::NotImplemented(
"Registering new schemas is not supported".to_string(),
))
}
/// Removes a schema from this catalog. Implementations of this method should return
/// errors if the schema exists but cannot be dropped. For example, in DataFusion's
/// default in-memory catalog, [`MemoryCatalogProvider`], a non-empty schema
/// will only be successfully dropped when `cascade` is true.
/// This is equivalent to how DROP SCHEMA works in PostgreSQL.
///
/// Implementations of this method should return None if schema with `name`
/// does not exist.
///
/// By default returns a "Not Implemented" error
fn deregister_schema(
&self,
_name: &str,
_cascade: bool,
) -> Result<Option<Arc<dyn SchemaProvider>>> {
Err(DataFusionError::NotImplemented(
"Deregistering new schemas is not supported".to_string(),
))
}
}
/// Simple in-memory implementation of a catalog.
pub struct MemoryCatalogProvider {
schemas: DashMap<String, Arc<dyn SchemaProvider>>,
}
impl MemoryCatalogProvider {
/// Instantiates a new MemoryCatalogProvider with an empty collection of schemas.
pub fn new() -> Self {
Self {
schemas: DashMap::new(),
}
}
}
impl CatalogProvider for MemoryCatalogProvider {
fn as_any(&self) -> &dyn Any {
self
}
fn schema_names(&self) -> Vec<String> {
self.schemas.iter().map(|s| s.key().clone()).collect()
}
fn schema(&self, name: &str) -> Option<Arc<dyn SchemaProvider>> {
self.schemas.get(name).map(|s| s.value().clone())
}
fn register_schema(
&self,
name: &str,
schema: Arc<dyn SchemaProvider>,
) -> Result<Option<Arc<dyn SchemaProvider>>> {
Ok(self.schemas.insert(name.into(), schema))
}
fn deregister_schema(
&self,
name: &str,
cascade: bool,
) -> Result<Option<Arc<dyn SchemaProvider>>> {
if let Some(schema) = self.schema(name) {
let table_names = schema.table_names();
match (table_names.is_empty(), cascade) {
(true, _) | (false, true) => {
let (_, removed) = self.schemas.remove(name).unwrap();
Ok(Some(removed))
}
(false, false) => Err(DataFusionError::Execution(format!(
"Cannot drop schema {} because other tables depend on it: {}",
name,
itertools::join(table_names.iter(), ", ")
))),
}
} else {
Ok(None)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::catalog::schema::MemorySchemaProvider;
use crate::datasource::empty::EmptyTable;
use crate::datasource::TableProvider;
use arrow::datatypes::Schema;
#[test]
fn default_register_schema_not_supported() {
// mimic a new CatalogProvider and ensure it does not support registering schemas
struct TestProvider {}
impl CatalogProvider for TestProvider {
fn as_any(&self) -> &dyn Any {
self
}
fn schema_names(&self) -> Vec<String> {
unimplemented!()
}
fn schema(&self, _name: &str) -> Option<Arc<dyn SchemaProvider>> {
unimplemented!()
}
}
let schema = Arc::new(MemorySchemaProvider::new()) as _;
let catalog = Arc::new(TestProvider {});
match catalog.register_schema("foo", schema) {
Ok(_) => panic!("unexpected OK"),
Err(e) => assert_eq!(e.to_string(), "This feature is not implemented: Registering new schemas is not supported"),
};
}
#[test]
fn memory_catalog_dereg_nonempty_schema() {
let cat = Arc::new(MemoryCatalogProvider::new()) as Arc<dyn CatalogProvider>;
let schema = Arc::new(MemorySchemaProvider::new()) as Arc<dyn SchemaProvider>;
let test_table = Arc::new(EmptyTable::new(Arc::new(Schema::empty())))
as Arc<dyn TableProvider>;
schema.register_table("t".into(), test_table).unwrap();
cat.register_schema("foo", schema.clone()).unwrap();
assert!(
cat.deregister_schema("foo", false).is_err(),
"dropping empty schema without cascade should error"
);
assert!(cat.deregister_schema("foo", true).unwrap().is_some());
}
#[test]
fn memory_catalog_dereg_empty_schema() {
let cat = Arc::new(MemoryCatalogProvider::new()) as Arc<dyn CatalogProvider>;
let schema = Arc::new(MemorySchemaProvider::new()) as Arc<dyn SchemaProvider>;
cat.register_schema("foo", schema.clone()).unwrap();
assert!(cat.deregister_schema("foo", false).unwrap().is_some());
}
#[test]
fn memory_catalog_dereg_missing() {
let cat = Arc::new(MemoryCatalogProvider::new()) as Arc<dyn CatalogProvider>;
assert!(cat.deregister_schema("foo", false).unwrap().is_none());
}
}