polars_plan/plans/
anonymous_scan.rs

1use std::any::Any;
2use std::fmt::{Debug, Formatter};
3
4use polars_core::prelude::*;
5
6pub use super::options::AnonymousScanOptions;
7use crate::dsl::Expr;
8
9pub struct AnonymousScanArgs {
10    pub n_rows: Option<usize>,
11    pub with_columns: Option<Arc<[PlSmallStr]>>,
12    pub schema: SchemaRef,
13    pub output_schema: Option<SchemaRef>,
14    pub predicate: Option<Expr>,
15}
16
17pub trait AnonymousScan: Send + Sync {
18    fn as_any(&self) -> &dyn Any;
19    /// Creates a DataFrame from the supplied function & scan options.
20    fn scan(&self, scan_opts: AnonymousScanArgs) -> PolarsResult<DataFrame>;
21
22    /// Produce the next batch Polars can consume. Implement this method to get proper
23    /// streaming support.
24    fn next_batch(&self, scan_opts: AnonymousScanArgs) -> PolarsResult<Option<DataFrame>> {
25        self.scan(scan_opts).map(Some)
26    }
27
28    /// function to supply the schema.
29    /// Allows for an optional infer schema argument for data sources with dynamic schemas
30    fn schema(&self, _infer_schema_length: Option<usize>) -> PolarsResult<SchemaRef> {
31        polars_bail!(ComputeError: "must supply either a schema or a schema function");
32    }
33    /// Specify if the scan provider should allow predicate pushdowns.
34    ///
35    /// Defaults to `false`
36    fn allows_predicate_pushdown(&self) -> bool {
37        false
38    }
39    /// Specify if the scan provider should allow projection pushdowns.
40    ///
41    /// Defaults to `false`
42    fn allows_projection_pushdown(&self) -> bool {
43        false
44    }
45    /// Specify if the scan provider should allow slice pushdowns.
46    ///
47    /// Defaults to `false`
48    fn allows_slice_pushdown(&self) -> bool {
49        false
50    }
51}
52
53impl Debug for dyn AnonymousScan {
54    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
55        write!(f, "anonymous_scan")
56    }
57}
polars_plan/plans/anonymous_scan.rs

polars_plan/plans/
anonymous_scan.rs
