Class ColumnWriter

java.lang.Object
dev.hardwood.writer.ColumnWriter
public final class ColumnWriter extends Object

Writes a Parquet file one aligned batch of columns at a time.

This is the columnar API: the shape for a caller that already holds columns — a query engine, an Arrow buffer, a bulk converter. Values are handed over as typed arrays addressed by leaf index or leaf path, an OPTIONAL column carrying its nulls as a Validity alongside them, and the writer shreds, pages, encodes and compresses them into the file.

try (ParquetFileWriter writer = ParquetFileWriter.create(out, schema)) {
    ColumnWriter columns = writer.columnWriter();
    columns.writeBatch(batch -> batch
            .longs("id", ids)
            .doubles("price", prices, priceNulls));
}

A ColumnWriter is not closeable: the ParquetFileWriter it came from owns the file, and closing it flushes the row group still buffered here along with the footer.

  • Method Details

    • writeBatch

      public void writeBatch(Consumer<ColumnBatch> filler) throws IOException

      Writes one aligned batch of column values, flushing row groups as the buffered data crosses the row-group target. A batch that would overflow the current row group is split at the boundary.

      The writer creates the batch — bound to the schema — passes it to filler to be populated (columns addressed by index or name), then submits it. There is no separate build or submit step to forget.

      Parameters:
      filler - populates the batch's columns; must cover every column exactly once
      Throws:
      IOException - if the write fails
      IllegalArgumentException - if the batch does not cover every column, or its per-layer inputs do not agree on a record count
      UnsupportedOperationException - if the schema has a shape the writer cannot produce
      IllegalStateException - if the writer is closed