crates/integrations/datafusion/src/system_tables/options.rs

// Licensed to the Apache Software Foundation (ASF) under one
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// distributed with this work for additional information
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// 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
//
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// under the License.

//! Mirrors Java [OptionsTable](https://github.com/apache/paimon/blob/release-1.3/paimon-core/src/main/java/org/apache/paimon/table/system/OptionsTable.java).

use std::any::Any;
use std::sync::{Arc, OnceLock};

use async_trait::async_trait;
use datafusion::arrow::array::{RecordBatch, StringArray};
use datafusion::arrow::datatypes::{DataType, Field, Schema, SchemaRef};
use datafusion::catalog::Session;
use datafusion::datasource::memory::MemorySourceConfig;
use datafusion::datasource::{TableProvider, TableType};
use datafusion::error::Result as DFResult;
use datafusion::logical_expr::Expr;
use datafusion::physical_plan::ExecutionPlan;
use paimon::table::Table;

pub(super) fn build(table: Table) -> DFResult<Arc<dyn TableProvider>> {
    Ok(Arc::new(OptionsTable { table }))
}

fn options_schema() -> SchemaRef {
    static SCHEMA: OnceLock<SchemaRef> = OnceLock::new();
    SCHEMA
        .get_or_init(|| {
            Arc::new(Schema::new(vec![
                Field::new("key", DataType::Utf8, false),
                Field::new("value", DataType::Utf8, false),
            ]))
        })
        .clone()
}

#[derive(Debug)]
struct OptionsTable {
    table: Table,
}

#[async_trait]
impl TableProvider for OptionsTable {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn schema(&self) -> SchemaRef {
        options_schema()
    }

    fn table_type(&self) -> TableType {
        TableType::View
    }

    async fn scan(
        &self,
        _state: &dyn Session,
        projection: Option<&Vec<usize>>,
        _filters: &[Expr],
        _limit: Option<usize>,
    ) -> DFResult<Arc<dyn ExecutionPlan>> {
        // Java uses LinkedHashMap insertion order; HashMap has none — sort for stable output.
        let mut entries: Vec<(&String, &String)> = self.table.schema().options().iter().collect();
        entries.sort_by(|a, b| a.0.cmp(b.0));

        let keys = StringArray::from_iter_values(entries.iter().map(|(k, _)| k.as_str()));
        let values = StringArray::from_iter_values(entries.iter().map(|(_, v)| v.as_str()));

        let schema = options_schema();
        let batch = RecordBatch::try_new(schema.clone(), vec![Arc::new(keys), Arc::new(values)])?;

        Ok(MemorySourceConfig::try_new_exec(
            &[vec![batch]],
            schema,
            projection.cloned(),
        )?)
    }
}