/Users/andrewlamb/Software/datafusion/datafusion/expr/src/table_source.rs
Line | Count | Source (jump to first uncovered line) |
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 |
7 | | // with the License. You may obtain a copy of the License at |
8 | | // |
9 | | // http://www.apache.org/licenses/LICENSE-2.0 |
10 | | // |
11 | | // Unless required by applicable law or agreed to in writing, |
12 | | // software distributed under the License is distributed on an |
13 | | // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
14 | | // KIND, either express or implied. See the License for the |
15 | | // specific language governing permissions and limitations |
16 | | // under the License. |
17 | | |
18 | | //! Table source |
19 | | |
20 | | use crate::{Expr, LogicalPlan}; |
21 | | |
22 | | use arrow::datatypes::SchemaRef; |
23 | | use datafusion_common::{Constraints, Result}; |
24 | | |
25 | | use std::{any::Any, borrow::Cow}; |
26 | | |
27 | | /// Indicates how a filter expression is handled by |
28 | | /// [`TableProvider::scan`]. |
29 | | /// |
30 | | /// Filter expressions are boolean expressions used to reduce the number of |
31 | | /// rows that are read from a table. Only rows that evaluate to `true` ("pass |
32 | | /// the filter") are returned. Rows that evaluate to `false` or `NULL` are |
33 | | /// omitted. |
34 | | /// |
35 | | /// [`TableProvider::scan`]: https://docs.rs/datafusion/latest/datafusion/datasource/provider/trait.TableProvider.html#tymethod.scan |
36 | | #[derive(Debug, Clone, PartialEq, Eq)] |
37 | | pub enum TableProviderFilterPushDown { |
38 | | /// The filter cannot be used by the provider and will not be pushed down. |
39 | | Unsupported, |
40 | | /// The filter can be used, but the provider might still return some tuples |
41 | | /// that do not pass the filter. |
42 | | /// |
43 | | /// In this case, DataFusion applies an additional `Filter` operation |
44 | | /// after the scan to ensure all rows are filtered correctly. |
45 | | Inexact, |
46 | | /// The provider **guarantees** that it will omit **only** tuples which |
47 | | /// pass the filter. |
48 | | /// |
49 | | /// In this case, DataFusion will not apply additional filtering. |
50 | | Exact, |
51 | | } |
52 | | |
53 | | /// Indicates the type of this table for metadata/catalog purposes. |
54 | | #[derive(Debug, Clone, Copy, PartialEq, Eq)] |
55 | | pub enum TableType { |
56 | | /// An ordinary physical table. |
57 | | Base, |
58 | | /// A non-materialised table that itself uses a query internally to provide data. |
59 | | View, |
60 | | /// A transient table. |
61 | | Temporary, |
62 | | } |
63 | | |
64 | | impl std::fmt::Display for TableType { |
65 | 0 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { |
66 | 0 | match self { |
67 | 0 | TableType::Base => write!(f, "Base"), |
68 | 0 | TableType::View => write!(f, "View"), |
69 | 0 | TableType::Temporary => write!(f, "Temporary"), |
70 | | } |
71 | 0 | } |
72 | | } |
73 | | |
74 | | /// Access schema information and filter push-down capabilities. |
75 | | /// |
76 | | /// The TableSource trait is used during logical query planning and |
77 | | /// optimizations and provides a subset of the functionality of the |
78 | | /// `TableProvider` trait in the (core) `datafusion` crate. The `TableProvider` |
79 | | /// trait provides additional capabilities needed for physical query execution |
80 | | /// (such as the ability to perform a scan). |
81 | | /// |
82 | | /// The reason for having two separate traits is to avoid having the logical |
83 | | /// plan code be dependent on the DataFusion execution engine. Some projects use |
84 | | /// DataFusion's logical plans and have their own execution engine. |
85 | | pub trait TableSource: Sync + Send { |
86 | | fn as_any(&self) -> &dyn Any; |
87 | | |
88 | | /// Get a reference to the schema for this table |
89 | | fn schema(&self) -> SchemaRef; |
90 | | |
91 | | /// Get primary key indices, if one exists. |
92 | 0 | fn constraints(&self) -> Option<&Constraints> { |
93 | 0 | None |
94 | 0 | } |
95 | | |
96 | | /// Get the type of this table for metadata/catalog purposes. |
97 | 0 | fn table_type(&self) -> TableType { |
98 | 0 | TableType::Base |
99 | 0 | } |
100 | | |
101 | | /// Tests whether the table provider can make use of any or all filter expressions |
102 | | /// to optimise data retrieval. |
103 | 0 | fn supports_filters_pushdown( |
104 | 0 | &self, |
105 | 0 | filters: &[&Expr], |
106 | 0 | ) -> Result<Vec<TableProviderFilterPushDown>> { |
107 | 0 | Ok((0..filters.len()) |
108 | 0 | .map(|_| TableProviderFilterPushDown::Unsupported) |
109 | 0 | .collect()) |
110 | 0 | } |
111 | | |
112 | | /// Get the Logical plan of this table provider, if available. |
113 | 0 | fn get_logical_plan(&self) -> Option<Cow<LogicalPlan>> { |
114 | 0 | None |
115 | 0 | } |
116 | | |
117 | | /// Get the default value for a column, if available. |
118 | 0 | fn get_column_default(&self, _column: &str) -> Option<&Expr> { |
119 | 0 | None |
120 | 0 | } |
121 | | } |