SQL Sink

StreamingFast Substreams SQL sink


Learn how to use the StreamingFast substreams-sink-sql tool with this documentation. A basic Substreams module example is provided to help you get started. We are going to showcase a Substreams module to extract data from the Ethereum blockchain and route it into a Protobuf for persistence in a SQL database.

The substreams-sink-sql today supports two database drivers namely PostgresSQL and Clickhouse. The tutorial below will focus on Postgres but we will describe how to connect to the other supported drivers.


1. Install substreams-sink-sql

Install substreams-sink-sql by using the pre-built binary release available in the official GitHub repository.

Extract substreams-sink-sql into a folder and ensure this folder is referenced globally via your PATH environment variable.

2. Set up accompanying code example

Access the accompanying code example for this tutorial in the official substreams-sink-sql repository. You will find the Substreams project for the tutorial in the docs/tutorial directory.

To create the required Protobuf files, run the included make protogen command.

make protogen

To ensure proper setup and functionality, use your installation of the substreams CLI to run the example code.

Use the make build and make stream_db commands to verify the setup for the example project. Use the included make command to build the Substreams module.

make build
make stream_db

Module handler for sink

The Rust source code file lib.rs contains an example code, the db_out module handler, which prepares and returns the module's DatabaseChanges output. The substreams-sink-sql tool captures the data sent out of the Substreams module and routes it into the appropriate columns and tables in the SQL database.

fn db_out(block_meta_start: store::Deltas<DeltaProto<BlockMeta>>) -> Result<DatabaseChanges, substreams::errors::Error> {
    let mut database_changes: DatabaseChanges = Default::default();
    transform_block_meta_to_database_changes(&mut database_changes, block_meta_start);

To gain a full understanding of the procedures and steps required for a database sink Substreams module, review the code in lib.rs. The complete code includes the addition of a Substreams store module and other helper functions related to the database.


The DatabaseChanges Protobuf definition can be viewed at the following link for a peek into the crates implementation.

When developing your Substreams, the Rust crate substreams-database-change can be used to create the required DatabaseChanges output type.

Note: An output type of proto:sf.substreams.sink.database.v1.DatabaseChanges is required by the map module in the Substreams manifest when working with this sink.

3. Install PostgreSQL

To proceed with this tutorial, you must have a working PostgreSQL installation. Obtain the software by downloading it from the vendor and install it by following the instructions for your operating system and platform.

If you encounter any issues, refer to the Troubleshooting Installation page on the official PostgreSQL Wiki for assistance.

4. Create example database

To store the blockchain data output by the Substreams module, you must create a new database in your PostgreSQL installation. The tutorial provides a schema and the PostgreSQL sink tool that handle the detailed aspects of the database design.

Use the psql command in your terminal to launch PostgreSQL.

Upon successful launch, you will see a prompt similar to the following, ready to accept commands for PostgreSQL.

psql (15.1)
Type "help" for help.


Use the following SQL command to create the example database:

CREATE DATABASE "substreams_example";

5. Create configuration file

Once the database has been created, you must now define the Substreams Sink Config in a Substreams manifest creating a deployable unit.

Let's create a folder sink and in it create a file called substreams.dev.yaml with the following content:

specVersion: v0.1.0
  name: "<name>"
  version: <version>

  sql: https://github.com/streamingfast/substreams-sink-sql/releases/download/protodefs-v1.0.1/substreams-sink-sql-protodefs-v1.0.1.spkg
  main: ../substreams.yaml

network: 'mainnet'

  module: main:db_out
  type: sf.substreams.sink.sql.v1.Service
    schema: "../schema.sql"
    wire_protocol_access: true

The package.name and package.version are meant to be replaced to fit your project.

The imports.main defines your Substreams manifest that you want to sink. The sink.module defines which import key (main here) and which module's name (db_out here).

The network field defines which network this deployment should be part of, in our case mainnet

The sink.type defines the type of the config that we are expecting, in our case it's sf.substreams.sink.sql.v1.Service (click on the link to see the message definition).

The sink.config is the instantiation of this sink.type with the config fully filled. Some config are special because they load from a file or from a folder. For example in our case the sink.config.schema is defined with a Protobuf option load_from_file which means the content of the ../schema.sql will actually be inlined in the Substreams manifest.

The final final can be found at sink/substreams.dev.yaml

6. Run setup command

Use the following command to run the substreams-sink-sql tool and set up the database for the tutorial.

substreams-sink-sql setup "psql://dev-node:insecure-change-me-in-prod@" ./sink/substreams.dev.yaml

The "psql://..." is the DSN (Database Source Name) containing the connection details to your database packed as an URL. The scheme (psql here) part of the DSN's url defines which driver to use, psql is what we are going to use here, see Drivers section below to see what other DSN you can use here.

The DSN's URL defines the database IP address, username, and password, which depend on your PostgreSQL installation. Adjust dev-node to your own username insecure-change-me-in-prod to your password and to where your database can be reached.


For DSN configuration for the currently supported drivers, see the list below:

7. Sink data to database

The substreams-sink-sql tool sinks data from the Substreams module to the SQL database. Use the tool's run command, followed by the endpoint to reach and your Substreams config file to use:

substreams-sink-sql run "psql://dev-node:insecure-change-me-in-prod@" ./sink/substreams.dev.yaml

The endpoint needs to match the blockchain targeted in the Substreams module. The example Substreams module uses the Ethereum blockchain.

Successful output from the substreams-sink-sql tool will resemble the following:

2023-01-18T12:32:19.107-0800 INFO (sink-sql) starting prometheus metrics server {"listen_addr": "localhost:9102"}
2023-01-18T12:32:19.107-0800 INFO (sink-sql) sink from psql {"dsn": "psql://dev-node:insecure-change-me-in-prod@", "endpoint": "mainnet.eth.streamingfast.io:443", "manifest_path": "substreams.yaml", "output_module_name": "db_out", "block_range": ""}
2023-01-18T12:32:19.107-0800 INFO (sink-sql) starting pprof server {"listen_addr": "localhost:6060"}
2023-01-18T12:32:19.127-0800 INFO (sink-sql) reading substreams manifest {"manifest_path": "sink/substreams.dev.yaml"}
2023-01-18T12:32:20.283-0800 INFO (pipeline) computed start block {"module_name": "store_block_meta_start", "start_block": 0}
2023-01-18T12:32:20.283-0800 INFO (pipeline) computed start block {"module_name": "db_out", "start_block": 0}
2023-01-18T12:32:20.283-0800 INFO (sink-sql) validating output store {"output_store": "db_out"}
2023-01-18T12:32:20.285-0800 INFO (sink-sql) resolved block range {"start_block": 0, "stop_block": 0}
2023-01-18T12:32:20.287-0800 INFO (sink-sql) ready, waiting for signal to quit
2023-01-18T12:32:20.287-0800 INFO (sink-sql) starting stats service {"runs_each": "2s"}
2023-01-18T12:32:20.288-0800 INFO (sink-sql) no block data buffer provided. since undo steps are possible, using default buffer size {"size": 12}
2023-01-18T12:32:20.288-0800 INFO (sink-sql) starting stats service {"runs_each": "2s"}
2023-01-18T12:32:20.730-0800 INFO (sink-sql) session init {"trace_id": "4605d4adbab0831c7505265a0366744c"}
2023-01-18T12:32:21.041-0800 INFO (sink-sql) flushing table rows {"table_name": "block_data", "row_count": 2}
2023-01-18T12:32:21.206-0800 INFO (sink-sql) flushing table rows {"table_name": "block_data", "row_count": 2}
2023-01-18T12:32:21.319-0800 INFO (sink-sql) flushing table rows {"table_name": "block_data", "row_count": 0}
2023-01-18T12:32:21.418-0800 INFO (sink-sql) flushing table rows {"table_name": "block_data", "row_count": 0}

Note: If you have an error looking like load psql table: retrieving table and schema: pq: SSL is not enabled on the server, it's because SSL is not enabled to reach you database, add ?sslmode=disable at the end of the sink.config.dsn value to connect without SSL.

You can view the database structure by using the following command, after launching PostgreSQL through the psql command.

<default_database_name>=# \c substreams_example

The table information is displayed in the terminal resembling the following:

           List of relations
 Schema |    Name    | Type  |  Owner
 public | block_data | table | postgres
 public | cursors    | table | postgres
(2 rows)

You can view the data extracted by Substreams and routed into the database table by using the following command:

substreams_example=# SELECT * FROM "block_data";

Output similar to the following is displayed in the terminal:

         id         | version |         at          | number |                               hash                               |                           parent_hash                            |      timestamp
 day:first:19700101 |         | 1970-01-01 00:00:00 | 0      | d4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3 | 0000000000000000000000000000000000000000000000000000000000000000 | 1970-01-01T00:00:00Z
 month:first:197001 |         | 1970-01-01 00:00:00 | 0      | d4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3 | 0000000000000000000000000000000000000000000000000000000000000000 | 1970-01-01T00:00:00Z
 day:first:20150730 |         | 2015-07-30 00:00:00 | 1      | 88e96d4537bea4d9c05d12549907b32561d3bf31f45aae734cdc119f13406cb6 | d4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3 | 2015-07-30T15:26:28Z
 month:first:201507 |         | 2015-07-01 00:00:00 | 1      | 88e96d4537bea4d9c05d12549907b32561d3bf31f45aae734cdc119f13406cb6 | d4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3 | 2015-07-30T15:26:28Z
 day:first:20150731 |         | 2015-07-31 00:00:00 | 6912   | ab79f822909750f88dfb9dd0350c1ebe98d5495e9c969cdeb6e0ac993b80175b | 8ffd8c04cb89ef45e0e1163639d51d9ed4fa03dd169db90123a1e047361b46fe | 2015-07-31T00:00:01Z
 day:first:20150801 |         | 2015-08-01 00:00:00 | 13775  | 2dcecad4cf2079d18169ca05bc21e7ba0add7132b9382984760f43f2761bd822 | abaabb8f8b7f7fa07668fb38fd5a08da9814cd8ad18a793e54eef6fa9b794ab4 | 2015-08-01T00:00:03Z
 month:first:201508 |         | 2015-08-01 00:00:00 | 13775  | 2dcecad4cf2079d18169ca05bc21e7ba0add7132b9382984760f43f2761bd822 | abaabb8f8b7f7fa07668fb38fd5a08da9814cd8ad18a793e54eef6fa9b794ab4 | 2015-08-01T00:00:03Z


When you use Substreams, it sends back a block to a consumer using an opaque cursor. This cursor points to the exact location within the blockchain where the block is. In case your connection terminates or the process restarts, upon re-connection, Substreams sends back the cursor of the last written bundle in the request so that the stream of data can be resumed exactly where it left off and data integrity is maintained.

You will find that the cursor is saved in the cursors table of the substreams_example database.


Insertion for historical blocks is performed in batched to increase ingestion speed. The --flush-interval flag can be used to change the default value of 1000 blocks. Also, the flag --live-block-time-delta <duration> can be used to change the delta at which we start considering blocks to be live, the logic is isLive = (now() - block.timestamp) < valueOfFlag(live-block-time-delta).

Conclusion and review

Routing data extracted from the blockchain using Substreams is a powerful and useful feature. With Substreams, you can route data to various types of sinks, including files and databases such as PostgreSQL. For more information on other types of sinks and sinking strategies, consult the core Substreams sinks documentation at https://substreams.streamingfast.io/developers-guide/substreams-sinks.

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