# regexp

## Description

Each input line is matched by regexp_pattern. Captures map positionally to target columns and convert to their types. regexp_skip_unmatched controls lines that do not match.

Input only. Select it with `FORMAT regexp`. Names ignore ASCII case; use the snake_case name shown here.

One complete physical line is matched at a time. Each capture group supplies the next target field; the capture's text is then decoded using regexp_escaping and converted to the target type.

The pattern must be supplied because its default is empty. A nonmatching line is an error unless regexp_skip_unmatched is enabled. This format has no output encoder.

```text
INSERT INTO table [(columns)] [SETTINGS ...] FORMAT regexp
<data>
```

## Example usage

```sql
SELECT name,is_input,is_output FROM system.formats WHERE name='regexp' FORMAT csv;
```

```text
"regexp",1,0
```

For lines such as `id: 7`, use `SETTINGS regexp_pattern='id: ([0-9]+)'` and one integer target column.

## Format settings

Use a statement `SETTINGS` clause; these options are not persisted by `SET`.

| Setting                 | Type     | Default | Meaning                                                                                                              |
| ----------------------- | -------- | ------- | -------------------------------------------------------------------------------------------------------------------- |
| `regexp_escaping`       | `String` | `Raw`   | Read captured fields as Raw text, Escaped text, Quoted literals, CSV fields, or JSON values.                         |
| `regexp_pattern`        | `String` | `''`    | Match every complete input line; one capture group supplies each target column. Empty requires a statement override. |
| `regexp_skip_unmatched` | `Bool`   | `0`     | Skip lines that do not match the expression; otherwise report their physical line number.                            |
| `snappy_mode`           | `String` | `basic` | Read Snappy client files as basic (Hadoop blocks) or framed (standard streaming format).                             |

## Load rows

Run the INSERT request separately; its remaining bytes are input data.

```sql
CREATE TABLE regexp_input(id UInt8);
```

```text
OK
```

```sql
INSERT INTO regexp_input SETTINGS regexp_pattern='id: ([0-9]+)' FORMAT regexp
id: 7
```

```text
OK
```

```sql
SELECT * FROM regexp_input FORMAT csv;
```

```text
7
```