datafusion_catalog/
schema.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
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8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
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14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18//! Describes the interface and built-in implementations of schemas,
19//! representing collections of named tables.
20
21use async_trait::async_trait;
22use datafusion_common::{exec_err, DataFusionError};
23use std::any::Any;
24use std::fmt::Debug;
25use std::sync::Arc;
26
27use crate::table::TableProvider;
28use datafusion_common::Result;
29
30/// Represents a schema, comprising a number of named tables.
31///
32/// Please see [`CatalogProvider`] for details of implementing a custom catalog.
33///
34/// [`CatalogProvider`]: super::CatalogProvider
35#[async_trait]
36pub trait SchemaProvider: Debug + Sync + Send {
37    /// Returns the owner of the Schema, default is None. This value is reported
38    /// as part of `information_tables.schemata
39    fn owner_name(&self) -> Option<&str> {
40        None
41    }
42
43    /// Returns this `SchemaProvider` as [`Any`] so that it can be downcast to a
44    /// specific implementation.
45    fn as_any(&self) -> &dyn Any;
46
47    /// Retrieves the list of available table names in this schema.
48    fn table_names(&self) -> Vec<String>;
49
50    /// Retrieves a specific table from the schema by name, if it exists,
51    /// otherwise returns `None`.
52    async fn table(
53        &self,
54        name: &str,
55    ) -> Result<Option<Arc<dyn TableProvider>>, DataFusionError>;
56
57    /// If supported by the implementation, adds a new table named `name` to
58    /// this schema.
59    ///
60    /// If a table of the same name was already registered, returns "Table
61    /// already exists" error.
62    #[allow(unused_variables)]
63    fn register_table(
64        &self,
65        name: String,
66        table: Arc<dyn TableProvider>,
67    ) -> Result<Option<Arc<dyn TableProvider>>> {
68        exec_err!("schema provider does not support registering tables")
69    }
70
71    /// If supported by the implementation, removes the `name` table from this
72    /// schema and returns the previously registered [`TableProvider`], if any.
73    ///
74    /// If no `name` table exists, returns Ok(None).
75    #[allow(unused_variables)]
76    fn deregister_table(&self, name: &str) -> Result<Option<Arc<dyn TableProvider>>> {
77        exec_err!("schema provider does not support deregistering tables")
78    }
79
80    /// Returns true if table exist in the schema provider, false otherwise.
81    fn table_exist(&self, name: &str) -> bool;
82}
datafusion_catalog/schema.rs

datafusion_catalog/
schema.rs
