Materialize Documentation
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CREATE SOURCE: JSON over PubNub

CREATE SOURCE connects Materialize to an external data source and lets you interact with its data as if the data were in a SQL table.

This document details how to connect Materialize to a JSON–formatted PubNub channel.

WARNING! PubNub sources are volatile. Please make sure you understand the limitations of volatile sources.

Conceptual framework

Sources represent connections to resources outside Materialize that it can read data from. For more information, see API Components: Sources.

Syntax

CREATE MATERIALIZED SOURCE IF NOT EXISTS src_name ( col_name , ) FROM PUBNUB SUBSCRIBE KEY key CHANNEL channel FORMAT TEXT ENVELOPE NONE

with_options

WITH ( field = val , )
Field Use
MATERIALIZED Materializes the source’s data, which retains all data in memory and makes sources directly selectable. For more information, see API Components: Materialized sources.
src_name The name for the source, which is used as its table name within SQL.
col_name Override default column name with the provided identifier. If used, a col_name must be provided for each column in the created source.
SUBSCRIBE KEY The secret subscription key for your PubNub account.
CHANNEL The name of the channel to subscribe to.
WITH ( option_list ) Options affecting source creation. For more detail, see WITH options.
TEXT Format the source’s data as ASCII-encoded text.
FORMAT BYTES Leave data received from the source as unformatted bytes, and store them in a column named data. However, you can easily transform the data to JSON. For more details, see Byte format details (JSON).
ENVELOPE NONE (Default) Use an append-only envelope. This means that records will only be appended and cannot be updated or deleted.

WITH options

The following options are valid within the WITH clause.

Field Value type Description
(No options supported.)

Details

PubNub source details

A PubNub source represents a subscription to a single PubNub channel. The subscribe key you provide must have permission to access the channel. For more details, see Permission Management in the PubNub documentation.

Text format details

Text-formatted sources reads lines from a file.

Raw byte format details

Raw byte-formatted sources provide Materialize the raw bytes received from the source without applying any formatting or decoding.

Raw byte-formatted sources have one column, which, by default, is named data.

Extracting JSON data from bytes

Materialize cannot receive JSON data directly from a source. Instead, you must create a source that stores the data it receives as raw bytes (FORMAT BYTES), and then construct views that provides access to your JSON data by casting the source’s bytea column (named data) to text, and then to jsonb.

CREATE MATERIALIZED VIEW jsonified_bytes AS
SELECT CAST(data AS JSONB) AS data
FROM (
    SELECT CONVERT_FROM(data, 'utf8') AS data
    FROM bytea_source
)

jsonb data expresses a JSON object similar to PostgreSQL’s implementation. For more information, see jsonb.

Append-only envelope

Append-only envelope means that all records received by the source is treated as an insert. This is Materialize’s default envelope (i.e. if no envelope is specified), and can be specified with ENVELOPE NONE.

Examples

PubNub market data

CREATE SOURCE market_orders_raw FROM PUBNUB
SUBSCRIBE KEY 'sub-c-4377ab04-f100-11e3-bffd-02ee2ddab7fe'
CHANNEL 'pubnub-market-orders';

This creates a source that…

To use this data in views, you can extract the message fields using Materialize’s jsonb functions:

CREATE MATERIALIZED VIEW market_orders AS
SELECT
    (text::jsonb)->>'bid_price' AS bid_price,
    (text::jsonb)->>'order_quantity' AS order_quantity,
    (text::jsonb)->>'symbol' AS symbol,
    (text::jsonb)->>'trade_type' AS trade_type,
    to_timestamp(((text::jsonb)->'timestamp')::bigint) AS timestamp
FROM market_orders_raw;
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