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5.3 KiB
5.3 KiB
slug |
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/en/operations/system-tables/part_log |
part_log
The system.part_log
table is created only if the part_log server setting is specified.
This table contains information about events that occurred with data parts in the MergeTree family tables, such as adding or merging data.
The system.part_log
table contains the following columns:
hostname
(LowCardinality(String)) — Hostname of the server executing the query.query_id
(String) — Identifier of theINSERT
query that created this data part.event_type
(Enum8) — Type of the event that occurred with the data part. Can have one of the following values:NewPart
— Inserting of a new data part.MergeParts
— Merging of data parts.DownloadPart
— Downloading a data part.RemovePart
— Removing or detaching a data part using DETACH PARTITION.MutatePart
— Mutating of a data part.MovePart
— Moving the data part from the one disk to another one.
merge_reason
(Enum8) — The reason for the event with typeMERGE_PARTS
. Can have one of the following values:NotAMerge
— The current event has the type other thanMERGE_PARTS
.RegularMerge
— Some regular merge.TTLDeleteMerge
— Cleaning up expired data.TTLRecompressMerge
— Recompressing data part with the.
merge_algorithm
(Enum8) — Merge algorithm for the event with typeMERGE_PARTS
. Can have one of the following values:Undecided
Horizontal
Vertical
event_date
(Date) — Event date.event_time
(DateTime) — Event time.event_time_microseconds
(DateTime64) — Event time with microseconds precision.duration_ms
(UInt64) — Duration.database
(String) — Name of the database the data part is in.table
(String) — Name of the table the data part is in.part_name
(String) — Name of the data part.partition_id
(String) — ID of the partition that the data part was inserted to. The column takes theall
value if the partitioning is bytuple()
.path_on_disk
(String) — Absolute path to the folder with data part files.rows
(UInt64) — The number of rows in the data part.size_in_bytes
(UInt64) — Size of the data part in bytes.merged_from
(Array(String)) — An array of names of the parts which the current part was made up from (after the merge).bytes_uncompressed
(UInt64) — Size of uncompressed bytes.read_rows
(UInt64) — The number of rows was read during the merge.read_bytes
(UInt64) — The number of bytes was read during the merge.peak_memory_usage
(Int64) — The maximum difference between the amount of allocated and freed memory in context of this thread.error
(UInt16) — The code number of the occurred error.exception
(String) — Text message of the occurred error.
The system.part_log
table is created after the first inserting data to the MergeTree
table.
Example
SELECT * FROM system.part_log LIMIT 1 FORMAT Vertical;
Row 1:
──────
hostname: clickhouse.eu-central1.internal
query_id: 983ad9c7-28d5-4ae1-844e-603116b7de31
event_type: NewPart
merge_reason: NotAMerge
merge_algorithm: Undecided
event_date: 2021-02-02
event_time: 2021-02-02 11:14:28
event_time_microseconds: 2021-02-02 11:14:28.861919
duration_ms: 35
database: default
table: log_mt_2
part_name: all_1_1_0
partition_id: all
path_on_disk: db/data/default/log_mt_2/all_1_1_0/
rows: 115418
size_in_bytes: 1074311
merged_from: []
bytes_uncompressed: 0
read_rows: 0
read_bytes: 0
peak_memory_usage: 0
error: 0
exception: