target-postgres

Target for Postgres.

Built with the Meltano SDK for Singer Taps and Targets.

Capabilities

• about
• stream-maps
• schema-flattening

Settings

Setting	Required	Default	Description
host	False	None	Hostname for postgres instance. Note if sqlalchemy_url is set this will be ignored.
port	False	5432	The port on which postgres is awaiting connection. Note if sqlalchemy_url is set this will be ignored.
user	False	None	User name used to authenticate. Note if sqlalchemy_url is set this will be ignored.
password	False	None	Password used to authenticate. Note if sqlalchemy_url is set this will be ignored.
database	False	None	Database name. Note if sqlalchemy_url is set this will be ignored.
sqlalchemy_url	False	None	SQLAlchemy connection string. This will override using host, user, password, port, dialect, and all ssl settings. Note that you must escape password special characters properly. See https://docs.sqlalchemy.org/en/20/core/engines.html#escaping-special-characters-such-as-signs-in-passwords
dialect+driver	False	postgresql+psycopg2	Dialect+driver see https://docs.sqlalchemy.org/en/20/core/engines.html. Generally just leave this alone. Note if sqlalchemy_url is set this will be ignored.
default_target_schema	False	melty	Postgres schema to send data to, example: tap-clickup
activate_version	False	True	If set to false, the tap will ignore activate version messages. If set to true, add_record_metadata must be set to true as well.
hard_delete	False	False	When activate version is sent from a tap this specefies if we should delete the records that don't match, or mark them with a date in the _sdc_deleted_at column. This config option is ignored if activate_version is set to false.
add_record_metadata	False	True	Note that this must be enabled for activate_version to work!This adds _sdc_extracted_at, _sdc_batched_at, and more to every table. See https://sdk.meltano.com/en/latest/implementation/record_metadata.html for more information.
ssl_enable	False	False	Whether or not to use ssl to verify the server's identity. Use ssl_certificate_authority and ssl_mode for further customization. To use a client certificate to authenticate yourself to the server, use ssl_client_certificate_enable instead. Note if sqlalchemy_url is set this will be ignored.
ssl_client_certificate_enable	False	False	Whether or not to provide client-side certificates as a method of authentication to the server. Use ssl_client_certificate and ssl_client_private_key for further customization. To use SSL to verify the server's identity, use ssl_enable instead. Note if sqlalchemy_url is set this will be ignored.
ssl_mode	False	verify-full	SSL Protection method, see postgres documentation for more information. Must be one of disable, allow, prefer, require, verify-ca, or verify-full. Note if sqlalchemy_url is set this will be ignored.
ssl_certificate_authority	False	~/.postgresql/root.crl	The certificate authority that should be used to verify the server's identity. Can be provided either as the certificate itself (in .env) or as a filepath to the certificate. Note if sqlalchemy_url is set this will be ignored.
ssl_client_certificate	False	~/.postgresql/postgresql.crt	The certificate that should be used to verify your identity to the server. Can be provided either as the certificate itself (in .env) or as a filepath to the certificate. Note if sqlalchemy_url is set this will be ignored.
ssl_client_private_key	False	~/.postgresql/postgresql.key	The private key for the certificate you provided. Can be provided either as the certificate itself (in .env) or as a filepath to the certificate. Note if sqlalchemy_url is set this will be ignored.
ssl_storage_directory	False	.secrets	The folder in which to store SSL certificates provided as raw values. When a certificate/key is provided as a raw value instead of as a filepath, it must be written to a file before it can be used. This configuration option determines where that file is created.
ssh_tunnel	False	None	SSH Tunnel Configuration, this is a json object
ssh_tunnel.enable	True (if ssh_tunnel set)	False	Enable an ssh tunnel (also known as bastion host), see the other ssh_tunnel.* properties for more details.
ssh_tunnel.host	True (if ssh_tunnel set)	False	Host of the bastion host, this is the host we'll connect to via ssh
ssh_tunnel.username	True (if ssh_tunnel set)	False	Username to connect to bastion host
ssh_tunnel.port	True (if ssh_tunnel set)	22	Port to connect to bastion host
ssh_tunnel.private_key	True (if ssh_tunnel set)	None	Private Key for authentication to the bastion host
ssh_tunnel.private_key_password	False	None	Private Key Password, leave None if no password is set
stream_maps	False	None	Config object for stream maps capability. For more information check out Stream Maps.
stream_map_config	False	None	User-defined config values to be used within map expressions.
flattening_enabled	False	None	'True' to enable schema flattening and automatically expand nested properties.
flattening_max_depth	False	None	The max depth to flatten schemas.

A full list of supported settings and capabilities is available by running: target-postgres --about

Installation

pipx install meltanolabs-target-postgres

Configuration

An Explanation of Various SSL Configuration Options

There are two distinct processes which both fall under the banner of SSL. One process occurs when the client wishes to ensure the identity of the server, and is the more common reason that SSL is used. Another is when the server wishes to ensure the identity of the client, for authentication/authorization purposes.

If your server is set up with a certificate and private key, and you wish to check their certificate against a root certificate which you posess, use ssl_enable. You may then further customize this process using the ssl_certificate_authority and ssl_mode settings. See the documentation for further details.

If your server is set up with a root certificate, and you wish to provide a certificate to the server to verify your identity, use ssl_client_certificate_enable. You may then further customize this process using the ssl_client_certificate and ssl_client_private_key settings. See the documentation for further details.

Configure using environment variables

This Singer target will automatically import any environment variables within the working directory's .env if the --config=ENV is provided, such that config values will be considered if a matching environment variable is set either in the terminal context or in the .env file.

Source Authentication and Authorization

The database account provided must have access to:

1. Create schemas
2. Create tables (DDL)
3. Push Data to tables (DML)

Usage

You can easily run target-postgres by itself or in a pipeline using Meltano.

Executing the Target Directly

target-postgres --version
target-postgres --help
# Test using the "Carbon Intensity" sample:
pipx install git+https://gitlab.com/meltano/tap-carbon-intensity
tap-carbon-intensity | target-postgres --config /path/to/target-postgres-config.json

Using Docker Compose

docker-compose.yml provides the commands to create two empty sample databases using Docker. These can be a starting point to create your own database running in Docker, or can be used to run the tap's built-in tests.

Developer Resources

Initialize your Development Environment

pipx install poetry
poetry install
pipx install pre-commit
pre-commit install

Setting Up SSL Files

We have set the provided keys in the .ssl directory to be valid for multiple centuries. However, we have also provided configuration instructions below to create all of the necessary files for testing SSL.

A list of each file and its purpose:

1. ca.crt: CA for client's certificate (stored on the server)
2. cert.crt: Client's certificate (stored on the client)
3. pkey.key: Client's private key (stored on the client)
4. public_pkey.key: Client's private key with incorrect file permissions (stored on the client)
5. root.crt: CA for server's certificate (stored on the client)
6. server.crt: Server's certificate (stored on the server)
7. server.key: Server's private key (stored on the server)

Run the following command to generate all relevant SSL files, with certificates valid for two centuries (73048 days).

openssl req -new -x509 -days 73048 -nodes -out ssl/server.crt -keyout ssl/server.key -subj "/CN=localhost" &&
openssl req -new -x509 -days 73048 -nodes -out ssl/cert.crt -keyout ssl/pkey.key -subj "/CN=postgres" &&
cp ssl/server.crt ssl/root.crt &&
cp ssl/cert.crt ssl/ca.crt &&
cp ssl/pkey.key ssl/public_pkey.key &&
chown 999:999 ssl/server.key &&
chmod 600 ssl/server.key &&
chmod 600 ssl/pkey.key &&
chmod 644 ssl/public_pkey.key

Now that all of the SSL files have been set up, you're ready to set up tests with pytest.

Create and Run Tests

Start the test databases using Docker Compose:

docker-compose up -d

Create tests within the target_postgres/tests subfolder and then run:

poetry run pytest

You can also test the target-postgres CLI interface directly using poetry run:

poetry run target-postgres --help

Testing with Meltano

Note: This target will work in any Singer environment and does not require Meltano. Examples here are for convenience and to streamline end-to-end orchestration scenarios.

Your project comes with a custom meltano.yml project file already created.

Next, install Meltano (if you haven't already) and any needed plugins:

# Install meltano
pipx install meltano
# Initialize meltano within this directory
meltano install

Now you can test and orchestrate using Meltano:

# Test invocation:
meltano invoke target-postgres --version

SDK Dev Guide

See the dev guide for more instructions on how to use the Meltano SDK to develop your own Singer taps and targets.

Data Types

The below table shows how this tap will map between jsonschema datatypes and Postgres datatypes.

jsonschema	Postgres
integer	bigint
UNSUPPORTED	bigserial
UNSUPPORTED	bit [ (n) ]
UNSUPPORTED	bit varying [ (n) ]
boolean	boolean
UNSUPPORTED	box
string with contentEncoding="base16" (opt-in feature)	bytea
UNSUPPORTED	character [ (n) ]
UNSUPPORTED	character varying [ (n) ]
UNSUPPORTED	cidr
UNSUPPORTED	circle
string with format="date"	date
UNSUPPORTED	double precision
UNSUPPORTED	inet
UNSUPPORTED	integer
UNSUPPORTED	interval [ fields ] [ (p) ]
UNSUPPORTED	json
array; object	jsonb
UNSUPPORTED	line
UNSUPPORTED	lseg
UNSUPPORTED	macaddr
UNSUPPORTED	macaddr8
UNSUPPORTED	money
number	numeric [ (p, s) ]
UNSUPPORTED	path
UNSUPPORTED	pg_lsn
UNSUPPORTED	pg_snapshot
UNSUPPORTED	point
UNSUPPORTED	polygon
UNSUPPORTED	real
UNSUPPORTED	smallint
UNSUPPORTED	smallserial
UNSUPPORTED	serial
string without format; untyped	text
string with format="time"	time [ (p) ] [ without time zone ]
UNSUPPORTED	time [ (p) ] with time zone
string with format="date-time"	timestamp [ (p) ] [ without time zone ]
UNSUPPORTED	timestamp [ (p) ] with time zone
UNSUPPORTED	tsquery
UNSUPPORTED	tsvector
UNSUPPORTED	txid_snapshot
string with format="uuid"	uuid
UNSUPPORTED	xml

Note that while object types are mapped directly to jsonb, array types are mapped to a jsonb array.

If a column has multiple jsonschema types, the following order is using to order Postgres types, from highest priority to lowest priority.

• BYTEA
• ARRAY(JSONB)
• JSONB
• TEXT
• TIMESTAMP
• DATETIME
• DATE
• TIME
• DECIMAL
• BIGINT
• INTEGER
• BOOLEAN
• NOTYPE

Content Encoding Support

Json Schema supports the contentEncoding keyword, which can be used to specify the encoding of input string types.

This target can detect content encoding clues in the schema to determine how to store the data in the postgres in a more efficient way.

Content encoding interpretation is disabled by default. This is because the default config is meant to be as permissive as possible, and do not make any assumptions about the data that could lead to data loss.

However if you know your data respects the advertised content encoding way, you can enable this feature to get better performance and storage efficiency.

To enable it, set the interpret_content_encoding option to True.

base16

The string is encoded using the base16 encoding, as defined in RFC 4648.

Example schema:

{
  "type": "object",
  "properties": {
    "my_hex": {
      "type": "string",
      "contentEncoding": "base16"
    }
  }
}

Data will be stored as a bytea in the database.

Example data:

# valid data
{ "my_hex": "01AF" }
{ "my_hex": "01af" }
{ "my_hex": "1af" }
{ "my_hex": "0x1234" }

# invalid data
{ "my_hex": " 0x1234 " }
{ "my_hex": "House" }

For convenience, data prefixed with 0x or containing an odd number of characters is supported although it's not part of the standard.