ClickHouse/docs/en/operations/table_engines/stripelog.md

# StripeLog

This engine belongs to the family of log engines. See the common properties of log engines and their differences in the [Log Engine Family](log_family.md) article.

Use this engine in scenarios when you need to write many tables with a small amount of data (less than 1 million rows).

## Creating a Table {#table_engines-stripelog-creating-a-table}

```
CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
(
    column1_name [type1] [DEFAULT|MATERIALIZED|ALIAS expr1],
    column2_name [type2] [DEFAULT|MATERIALIZED|ALIAS expr2],
    ...
) ENGINE = StripeLog
```

See the detailed description of the [CREATE TABLE](../../query_language/create.md#create-table-query) query.

## Writing the Data {#table_engines-stripelog-writing-the-data}

The `StripeLog` engine stores all the columns in one file. For each `INSERT` query, ClickHouse appends the data block to the end of a table file, writing columns one by one.

For each table ClickHouse writes the files:

- `data.bin` — Data file.
- `index.mrk` — File with marks. Marks contain offsets for each column of each data block inserted.

The `StripeLog` engine does not support the `ALTER UPDATE` and `ALTER DELETE` operations.

## Reading the Data {#table_engines-stripelog-reading-the-data}

The file with marks allows ClickHouse to parallelize the reading of data. This means that a `SELECT` query returns rows in an unpredictable order. Use the `ORDER BY` clause to sort rows.

## Example of Use {#table_engines-stripelog-example-of-use}

Creating a table:

```sql
CREATE TABLE stripe_log_table
(
    timestamp DateTime,
    message_type String,
    message String
)
ENGINE = StripeLog
```

Inserting data:

```sql
INSERT INTO stripe_log_table VALUES (now(),'REGULAR','The first regular message')
INSERT INTO stripe_log_table VALUES (now(),'REGULAR','The second regular message'),(now(),'WARNING','The first warning message')
```

We used two `INSERT` queries to create two data blocks inside the `data.bin` file.

ClickHouse uses multiple threads when selecting data. Each thread reads a separate data block and returns resulting rows independently as it finishes. As a result, the order of blocks of rows in the output does not match the order of the same blocks in the input in most cases. For example:

```sql
SELECT * FROM stripe_log_table
```
```
┌───────────timestamp─┬─message_type─┬─message────────────────────┐
│ 2019-01-18 14:27:32 │ REGULAR      │ The second regular message │
│ 2019-01-18 14:34:53 │ WARNING      │ The first warning message  │
└─────────────────────┴──────────────┴────────────────────────────┘
┌───────────timestamp─┬─message_type─┬─message───────────────────┐
│ 2019-01-18 14:23:43 │ REGULAR      │ The first regular message │
└─────────────────────┴──────────────┴───────────────────────────┘
```

Sorting the results (ascending order by default):

```sql
SELECT * FROM stripe_log_table ORDER BY timestamp
```
```
┌───────────timestamp─┬─message_type─┬─message────────────────────┐
│ 2019-01-18 14:23:43 │ REGULAR      │ The first regular message  │
│ 2019-01-18 14:27:32 │ REGULAR      │ The second regular message │
│ 2019-01-18 14:34:53 │ WARNING      │ The first warning message  │
└─────────────────────┴──────────────┴────────────────────────────┘
```

[Original article](https://clickhouse.yandex/docs/en/operations/table_engines/stripelog/) <!--hide-->