nordisk/skade

vendor/iceberg-arrow59/src/cow_rewrite/rewriter.rs

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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// under the License.

use arrow_array::RecordBatch;

use crate::Result;

/// Result of rewriting a single record batch.
#[derive(Debug)]
pub struct CowBatchRewrite {
    /// Rewritten output batch, or `None` when the input batch is fully removed.
    ///
    /// Output batches must use the same schema as their input batch — the
    /// planned snapshot's schema, which may be older than the table's current
    /// schema. Rewriters must also preserve each source file's partition
    /// values: this primitive writes replacements into the source file's
    /// partition and does not repartition rows.
    pub output: Option<RecordBatch>,
    /// Whether the rewrite changed the input batch contents.
    ///
    /// Set this to `true` whenever `output` differs from the input batch,
    /// including filtered rows, updated values, reordered rows, or `None`.
    pub changed: bool,
}

/// Rewrites record batches for copy-on-write operations.
///
/// `rewrite_batch` is synchronous: it runs on the async runtime thread that
/// drives the read/write pipeline, so implementations must not perform
/// blocking work — async I/O such as catalog enrichment or cross-table
/// lookups is not supported in this contract. The method stays sync (rather
/// than returning a boxed future) so the trait remains object safe for
/// `Arc<dyn CowBatchRewriter>`.
pub trait CowBatchRewriter: Send + Sync {
    /// Rewrites a record batch and reports whether it changed.
    ///
    /// `output: None` means the batch is fully removed, which is itself a
    /// change: the orchestrator treats it as changed regardless of the
    /// `changed` flag, so a rewriter cannot accidentally keep dropped rows
    /// alive by reporting `changed: false` alongside a `None` output.
    fn rewrite_batch(&self, batch: RecordBatch) -> Result<CowBatchRewrite>;
}