tap-redshift 1.0.0b1

Singer.io tap for extracting data from redshift

Singer tap that extracts data from a Redshift database and produces JSON-formatted data following the Singer spec.

Usage

tap-redshift assumes you have connection to redshift.

Create a configuration file

When you install tap-redshift, you need to create a config.json file for the database connection.

The json file requires the following attributes;

• host

• port

• dbname

• user

• password

And an optional attribute;

• schema

Example:

{
    "host": "REDSHIFT_HOSTT",
    "port": "REDSHIFT_PORT",
    "dbname": "REDSHIFT_DBNAME",
    "user": "REDSHIFT_USER",
    "password": "REDSHIFT_PASSWORD",
    "schema": "REDSHIFT_SCHEMA"
}

Discovery mode

The tap can be invoked in discovery mode to get the available tables and columns in the database. It points to the config file created to connect to redshift:

$ tap-redshift --config config.json -d

A full catalog tap is writtem to stdout, with a JSON-schema description of each table. A source table directly corresponds to a Singer stream.

Redirect output from the tap’s discovery mode to a file so that it can be modified when the tap is to be invoked in sync mode.

$ tap-redshift -c config.json -d > properties.json

This runs the tap in discovery mode and copies the output into a properties.json file.

Tables and property selection

In sync mode, tap-redshift consumes a modified version of the catalog where tables and fields have been marked as selected.

Edit properties.json file to make selections by adding key-value of "selected": "true" to the top level schema and also in the metadata for each properties you want to select.

Example:

{
    "tap_stream_id": "sample-stream-id",
    "table_name": "sample-name",
    "stream": "sample-stream",
    "is_view": false,
    "database_name": "sample-dbname"
    "schema": {
        "selected": "true",
        "properties": {
            "name": {
                "maxLength": 255,
                "inclusion": "available",
                "type": [
                    "null",
                    "string"
                ]
            },
            "id": {
                "minimum": -2147483648,
                "inclusion": "automatic",
                "maximum": 2147483647,
                "type": [
                    "null",
                    "integer"
                ]
            }
        },
        "type": "object"
    },
    "metadata": [
        {
            "metadata": {
                "selected": true,
                "selected-by-default": true,
                "sql-datatype": "int2"
            },
            "breadcrumb": [
                "properties",
                "id"
            ]
        },
        {
            "metadata": {
                "selected": true,
                "selected-by-default": true,
                "sql-datatype": "varchar"
            },
            "breadcrumb": [
                "properties",
                "catname"
            ]
        },
    ]
}

The tap can then be invoked in sync mode with the properties catalog argument:

$ tap-redshift -c config.json --properties properties.json

Replication methods and state file

There are two ways to replicate a given table. FULL_TABLE and INCREMENTAL. FULL_TABLE replication is used by default.

Full Table

Full-table replication extracts all data from the source table each time the tap is invoked without a state file.

Incremental

Incremental replication works in conjunction with a state file to only extract new records each time the tap is invoked i.e continue from the last synced data.

To use incremental replication, we need to add the replication_method and replication_key to the top level of the properties.json file.

{
    "streams": [
        {
            "replication_method": "INCREMENTAL",
            "replication_key": "id",
            "tap_stream_id": "tap-sample",
            "schema": {
                "properties": {
                    "name": {
                        "selected": "true",
                        "maxLength": 255,
                        "inclusion": "available",
                        "type": [
                            "null",
                            "string"
                        ]
                    },
                    "id": {
                        "selected": "true",
                        "minimum": -2147483648,
                        "inclusion": "automatic",
                        "maximum": 2147483647,
                        "type": [
                            "null",
                            "integer"
                        ]
                    }
                }
                "type": "object"
            }
        }
    ]
}

We can then invoke the tap again in sync mode. This time the output will have STATE messages that contains a replication_key_value and bookmark for data that were extracted.

Redirect the output to a state.json file. Normally, the target will echo the last STATE after it has finished processing data.

Run the code below to pass the state into a state.json file and then grab the last synced state data.

$ tap-redshift -c config.json --properties properties.json > state.json

$ tail -1 state.json > state.json.tmp && mv state.json.tmp state.json

The state.json file should look like;

{
    "currently_syncing": "dbname-tablename",
    "bookmarks": {
        "dev-category": {
            "replication_key": "id",
            "version": 1516304171710,
            "replication_key_value": 3
        }
    }
}

We can then always invoke the incremental replication with the state.json file to only sync new data created after the last synced data.

$ tap-redshift -c config.json --properties properties.json --state state.json