# Generic JDBC input plugin for Embulk

Generic JDBC input plugin for Embulk loads records from a database using a JDBC driver. If the database follows ANSI SQL standards and JDBC standards strictly, this plugin works. But because of many incompatibilities, use case of this plugin is very limited. It's recommended to use specific plugins for the databases.

## Overview

* **Plugin type**: input
* **Resume supported**: yes

## Configuration

- **driver_path**: path to the jar file of the JDBC driver (e.g. 'sqlite-jdbc-3.8.7.jar') (string, optional)
- **driver_class**: class name of the JDBC driver (e.g. 'org.sqlite.JDBC') (string, required)
- **url**: URL of the JDBC connection (e.g. 'jdbc:sqlite:mydb.sqlite3') (string, required)
- **user**: database login user name (string, optional)
- **password**: database login password (string, default: optional)
- **ssl**: use SSL to connect to the database (string, default: `disable`. `enable` uses SSL without server-side validation and `verify` checks the certificate. For compatibility reasons, `true` behaves as `enable` and `false` behaves as `disable`.)
- **schema**: destination schema name (string, default: use the default schema)
- **fetch_rows**: number of rows to fetch one time (integer, default: 10000)
- **connect_timeout**: not supported.
- **socket_timeout**: timeout for executing the query. 0 means no timeout. (integer (seconds), default: 1800)
- **options**: extra JDBC properties (hash, default: {})
- If you write SQL directly,
  - **query**: SQL to run (string)
  - **use_raw_query_with_incremental**: If true, you can write optimized query using prepared statement. See [Use incremental loading with raw query](#use-incremental-loading-with-raw-query) for more detail (boolean, default: false)
- If **query** is not set,
  - **table**: destination table name (string, required)
  - **select**: expression of select (e.g. `id, created_at`) (string, default: "*")
  - **where**: WHERE condition to filter the rows (string, default: no-condition)
  - **order_by**: expression of ORDER BY to sort rows (e.g. `created_at DESC, id ASC`) (string, default: not sorted)
- **default_timezone**: If the sql type of a column is `date`/`time`/`datetime` and the embulk type is `string`, column values are formatted int this default_timezone. You can overwrite timezone for each columns using column_options option. (string, default: `UTC`)
- **default_column_options**: column_options for each JDBC type as default. Key is a JDBC type (e.g. 'DATE', 'BIGINT'). Value is same as column_options's value.
- **column_options**: advanced: a key-value pairs where key is a column name and value is options for the column.
  - **value_type**: embulk get values from database as this value_type. Typically, the value_type determines `getXXX` method of `java.sql.PreparedStatement`. `value_type: json` is an exception which uses `getString` and parses the result as a JSON string.
  (string, default: depends on the sql type of the column. Available values options are: `long`, `double`, `float`, `decimal`, `boolean`, `string`, `json`, `date`, `time`, `timestamp`)
  - **type**: Column values are converted to this embulk type.
  Available values options are: `boolean`, `long`, `double`, `string`, `json`, `timestamp`).
  By default, the embulk type is determined according to the sql type of the column (or value_type if specified).
  - **timestamp_format**: If the sql type of the column is `date`/`time`/`datetime` and the embulk type is `string`, column values are formatted by this timestamp_format. And if the embulk type is `timestamp`, this timestamp_format may be used in the output plugin. For example, stdout plugin use the timestamp_format, but *csv formatter plugin doesn't use*. (string, default : `%Y-%m-%d` for `date`, `%H:%M:%S` for `time`, `%Y-%m-%d %H:%M:%S` for `timestamp`)
  - **timezone**: If the sql type of the column is `date`/`time`/`datetime` and the embulk type is `string`, column values are formatted in this timezone.
(string, value of default_timezone option is used by default)
- **after_select**: if set, this SQL will be executed after the SELECT query in the same transaction.


## Incremental loading

Incremental loading uses monotonically increasing unique columns (such as auto-increment id) to load records inserted (or updated) after last execution.

First, if `incremental: true` is set, this plugin loads all records with additional ORDER BY. For example, if `incremental_columns: [updated_at, id]` option is set, query will be as following:

```
SELECT * FROM (
  ...original query is here...
)
ORDER BY updated_at, id
```

When bulk data loading finishes successfully, it outputs `last_record: ` paramater as config-diff so that next execution uses it.

At the next execution, when `last_record: ` is also set, this plugin generates additional WHERE conditions to load records larger than the last record. For example, if `last_record: ["2017-01-01 00:32:12", 5291]` is set,

```
SELECT * FROM (
  ...original query is here...
)
WHERE updated_at > '2017-01-01 00:32:12' OR (updated_at = '2017-01-01 00:32:12' AND id > 5291)
ORDER BY updated_at, id
```

Then, it updates `last_record: ` so that next execution uses the updated last_record.

**IMPORTANT**: If you set `incremental_columns: ` option, make sure that there is an index on the columns to avoid full table scan. For this example, following index should be created:

```
CREATE INDEX embulk_incremental_loading_index ON table (updated_at, id);
```

Recommended usage is to leave `incremental_columns` unset and let this plugin automatically finds an auto-increment primary key. Currently, only strings and integers are supported as incremental_columns.

### Use incremental loading with raw query

**IMPORTANT**: This is an advanced feature and assume you have an enough knowledge about incremental loading using Embulk and this plugin

Normally, you can't write your own query for incremental loading.
`use_raw_query_with_incremental` option allow you to write raw query for incremental loading. It might be well optimized and faster than SQL statement which is automatically generated by plugin.

Prepared statement starts with `:` is available instead of fixed value.
`last_record` value is necessary when you use this option.
Please use prepared statement that is well distinguishable in SQL statement. Using too simple prepared statement like `:a` might cause SQL parse failure.

In the following example, prepared statement `:foo_id` will be replaced with value "1" which is specified in `last_record`.

```yaml
in:
  type: jdbc
  query:
    SELECT
      foo.id as foo_id, bar.name
    FROM
      foo LEFT JOIN bar ON foo.id = bar.id
    WHERE
      foo.hoge IS NOT NULL
      AND foo.id > :foo_id
    ORDER BY
      foo.id ASC
  use_raw_query_with_incremental: true
  incremental_columns:
    - foo_id
  incremental: true
  last_record: [1]
```

## Example

```yaml
in:
  type: jdbc
  driver_path: /opt/oracle/ojdbc6.jar
  driver_class: oracle.jdbc.driver.OracleDriver
  url: jdbc:oracle:thin:@127.0.0.1:1521:mydb
  user: myuser
  password: "mypassword"
  table: "my_table"
  select: "col1, col2, col3"
  where: "col4 != 'a'"
  order_by: "col1 DESC"
```

This configuration will generate following SQL:

```
SELECT col1, col2, col3
FROM "my_table"
WHERE col4 != 'a'
ORDER BY col1 DESC
```

If you need a complex SQL,

```yaml
in:
  type: jdbc
  driver_path: /opt/oracle/ojdbc6.jar
  driver_class: oracle.jdbc.driver.OracleDriver
  url: jdbc:oracle:thin:@127.0.0.1:1521:mydb
  user: myuser
  password: "mypassword"
  query: |
    SELECT t1.id, t1.name, t2.id AS t2_id, t2.name AS t2_name
    FROM table1 AS t1
    LEFT JOIN table2 AS t2
      ON t1.id = t2.t1_id
```

Advanced configuration:

```yaml
in:
  type: jdbc
  driver_path: /opt/oracle/ojdbc6.jar
  driver_class: oracle.jdbc.driver.OracleDriver
  url: jdbc:oracle:thin:@127.0.0.1:1521:mydb
  user: myuser
  password: "mypassword"
  table: "my_table"
  select: "col1, col2, col3"
  where: "col4 != 'a'"
  default_column_options:
    DATE: { type: string, timestamp_format: "%Y/%m/%d", timezone: "+0900"}
    BIGINT: { type: string }
  column_options:
    col1: {type: long}
    col3: {type: string, timestamp_format: "%Y/%m/%d", timezone: "+0900"}
  after_select: "update my_table set col5 = '1' where col4 != 'a'"

```

## Build

```
$ ./gradlew gem
```