docs/UserGuide/Data-Concept/Time-Partition.md

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# Time partition

## Features

Time partition divides data according to time, and a time partition is used to save all data within a certain time range. The time partition number is represented by a natural number. Number 0 means January 1, 1970, it will increase by one every partition_interval milliseconds. Time partition number's calculation formula is timestamp / partition_interval. The main configuration items are as follows:

* time\_partition\_interval

|Name| time\_partition\_interval                                                              |
 |:---:|:-------------------------------------------------------------------------------------------------------|
|Description| Time range for dividing database, time series data will be divided into groups by this time range |
|Type| Int64                                                                                                  |
|Default| 604800000                                                                                               |
|Effective| Only allowed to be modified in first start up                                                          |

## Configuration example

Enable time partition and set partition_interval to 86400000 (one day), then the data distribution is shown as the following figure:

<img style="width:100%; max-width:800px; max-height:600px; margin-left:auto; margin-right:auto; display:block;" src="https://github.com/apache/iotdb-bin-resources/blob/main/docs/UserGuide/Data%20Concept/Time-Partition/time_partition_example.png?raw=true" alt="time partition example">

* Insert one datapoint with timestamp 0, calculate 0/86400000 = 0, then this datapoint will be stored in TsFile under folder 0

* Insert one datapoint with timestamp 1609459200010, calculate 1609459200010/86400000 = 18628, then this datapoint will be stored in TsFile under folder 18628

## Suggestions

When enabling time partition, it is better to enable timed flush memtable, configuration params are detailed in [Config manual for timed flush](../Reference/DataNode-Config-Manual.md).

* enable_timed_flush_unseq_memtable: Whether to enable timed flush unsequence memtable, enabled by default.

* enable_timed_flush_seq_memtable: Whether to enable timed flush sequence memtable, disabled by default. It should be enabled when time partition is enabled, so inactive time partition's memtable can be flushed regularly.