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feat: Make FanoutWriter writer configurable #1872

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feat: Make FanoutWriter writer configurable #1872

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7f90197
feat: Make `FanoutWriter` writer configurable
jonathanc-n Nov 19, 2025
4308d09
Add to `TableProperties` struct
jonathanc-n Nov 20, 2025
e8ec13c
Merge branch 'main' into add-fanout_enabled-to-table-properties
jonathanc-n Nov 20, 2025
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13 changes: 13 additions & 0 deletions crates/iceberg/src/spec/table_properties.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,8 @@ pub struct TableProperties {
pub write_format_default: String,
/// The target file size for files.
pub write_target_file_size_bytes: usize,
/// Whether to use `FanoutWriter` for partitioned tables.
pub write_fanout_enabled: bool,
}

impl TableProperties {
Expand Down Expand Up @@ -137,6 +139,12 @@ impl TableProperties {
pub const PROPERTY_WRITE_TARGET_FILE_SIZE_BYTES: &str = "write.target-file-size-bytes";
/// Default target file size
pub const PROPERTY_WRITE_TARGET_FILE_SIZE_BYTES_DEFAULT: usize = 512 * 1024 * 1024; // 512 MB

/// Whether to use `FanoutWriter` for partitioned tables (handles unsorted data).
/// If false, uses `ClusteredWriter` (requires sorted data, more memory efficient).
pub const PROPERTY_WRITE_FANOUT_ENABLED: &str = "write.fanout.enabled";
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@CTTY CTTY Nov 19, 2025

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I think write.datafusion.fanout.enabled will be a better property name since Java has

public static final String SPARK_WRITE_PARTITIONED_FANOUT_ENABLED = "write.spark.fanout.enabled";

/// Default value for fanout writer enabled
pub const PROPERTY_WRITE_FANOUT_ENABLED_DEFAULT: bool = true;
}

impl TryFrom<&HashMap<String, String>> for TableProperties {
Expand Down Expand Up @@ -175,6 +183,11 @@ impl TryFrom<&HashMap<String, String>> for TableProperties {
TableProperties::PROPERTY_WRITE_TARGET_FILE_SIZE_BYTES,
TableProperties::PROPERTY_WRITE_TARGET_FILE_SIZE_BYTES_DEFAULT,
)?,
write_fanout_enabled: parse_property(
props,
TableProperties::PROPERTY_WRITE_FANOUT_ENABLED,
TableProperties::PROPERTY_WRITE_FANOUT_ENABLED_DEFAULT,
)?,
})
}
}
Expand Down
22 changes: 20 additions & 2 deletions crates/integrations/datafusion/src/physical_plan/write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -266,8 +266,26 @@ impl ExecutionPlan for IcebergWriteExec {
let data_file_writer_builder = DataFileWriterBuilder::new(rolling_writer_builder);

// Create TaskWriter
// TODO: Make fanout_enabled configurable via table properties
let fanout_enabled = true;
let fanout_enabled = self
.table
.metadata()
.properties()
.get(TableProperties::PROPERTY_WRITE_FANOUT_ENABLED)
.map(|value| {
value
.parse::<bool>()
.map_err(|e| {
Error::new(
ErrorKind::DataInvalid,
"Invalid value for write.fanout.enabled, expected 'true' or 'false'",
)
.with_source(e)
})
.map_err(to_datafusion_error)
})
.transpose()?
.unwrap_or(TableProperties::PROPERTY_WRITE_FANOUT_ENABLED_DEFAULT);

let schema = self.table.metadata().current_schema().clone();
let partition_spec = self.table.metadata().default_partition_spec().clone();
let task_writer = TaskWriter::try_new(
Expand Down
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