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system.merges

Querying in ClickHouse Cloud

The data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the clusterAllReplicas function. See here for further details.

Contains information about merges and part mutations currently in process for tables in the MergeTree family.

Columns:

  • database (String) — The name of the database the table is in.
  • table (String) — Table name.
  • elapsed (Float64) — The time elapsed (in seconds) since the merge started.
  • progress (Float64) — The percentage of completed work from 0 to 1.
  • num_parts (UInt64) — The number of parts to be merged.
  • source_part_names (Array(String)) — The list of source parts names.
  • result_part_name (String) — The name of the part that will be formed as the result of merging.
  • source_part_paths (Array(String)) — The list of paths for each source part.
  • result_part_path (String) — The path of the part that will be formed as the result of merging.
  • partition_id (String) — The identifier of the partition where the merge is happening.
  • partition (String) — The name of the partition
  • is_mutation (UInt8) — 1 if this process is a part mutation.
  • total_size_bytes_compressed (UInt64) — The total size of the compressed data in the merged chunks.
  • total_size_bytes_uncompressed (UInt64) — The total size of compressed data in the merged chunks.
  • total_size_marks (UInt64) — The total number of marks in the merged parts.
  • bytes_read_uncompressed (UInt64) — Number of bytes read, uncompressed.
  • rows_read (UInt64) — Number of rows read.
  • bytes_written_uncompressed (UInt64) — Number of bytes written, uncompressed.
  • rows_written (UInt64) — Number of rows written.
  • columns_written (UInt64) — Number of columns written (for Vertical merge algorithm).
  • memory_usage (UInt64) — Memory consumption of the merge process.
  • thread_id (UInt64) — Thread ID of the merge process.
  • merge_type (String) — The type of current merge. Empty if it's an mutation.
  • merge_algorithm (String) — The algorithm used in current merge. Empty if it's an mutation.