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ComputePartitionStats

The ComputePartitionStats action computes and writes partition statistics for an Iceberg table. This action helps optimize query planning by providing metadata about partition-level data characteristics.

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Interface

public interface ComputePartitionStats extends Action<ComputePartitionStats, ComputePartitionStats.Result>

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Overview

Partition statistics provide valuable metadata that query engines can use to optimize execution plans. The action:
  • Computes statistics for partitions in a table snapshot
  • Writes statistics to a dedicated statistics file
  • Uses the current snapshot by default
  • Can target a specific snapshot if needed

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Methods

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snapshot

Choose a specific table snapshot to compute partition statistics. 
ComputePartitionStats snapshot(long snapshotId)
Parameters:
  • snapshotId - The ID of the snapshot for which stats need to be computed
Returns: this for method chaining Example: 
action.snapshot(1234567890L);
If not specified, the action uses the current snapshot of the table.

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Result

The Result interface provides information about the computed statistics.

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Methods

interface Result {
  PartitionStatisticsFile statisticsFile();
}

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statisticsFile

Returns the statistics file that was written, or null if no statistics were collected. Returns: PartitionStatisticsFile or null

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Usage Examples

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Compute Stats for Current Snapshot

// Compute partition statistics for the current snapshot
ComputePartitionStats.Result result = actions
  .computePartitionStats(table)
  .execute();

PartitionStatisticsFile statsFile = result.statisticsFile();
if (statsFile != null) {
  System.out.println("Statistics file: " + statsFile.path());
  System.out.println("Snapshot ID: " + statsFile.snapshotId());
}

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Compute Stats for Specific Snapshot

// Compute partition statistics for a specific snapshot
long targetSnapshotId = table.currentSnapshot().parentId();

ComputePartitionStats.Result result = actions
  .computePartitionStats(table)
  .snapshot(targetSnapshotId)
  .execute();

if (result.statisticsFile() != null) {
  System.out.println("Computed stats for snapshot: " + targetSnapshotId);
}

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Check Statistics File Details

// Compute stats and examine the results
ComputePartitionStats.Result result = actions
  .computePartitionStats(table)
  .execute();

PartitionStatisticsFile statsFile = result.statisticsFile();
if (statsFile != null) {
  System.out.println("Statistics Details:");
  System.out.println("  Path: " + statsFile.path());
  System.out.println("  Snapshot: " + statsFile.snapshotId());
  System.out.println("  Size: " + statsFile.fileSizeInBytes() + " bytes");
} else {
  System.out.println("No statistics were collected");
}

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Best Practices

  1. Compute after significant data changes: Run this action after major writes or rewrites to keep statistics current
  2. Use with query optimization: Ensure your query engine is configured to use partition statistics
  3. Monitor statistics freshness: Outdated statistics may lead to suboptimal query plans
  4. Consider snapshot selection: For historical analysis, compute stats on specific snapshots
Partition statistics are most beneficial for partitioned tables with selective query patterns.