Materialize Documentation
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CREATE SOURCE: CSV from local file

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 local CSV files.

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 , , key_constraint ) FROM FILE path COMPRESSION NONE GZIP with_options FORMAT CSV WITH HEADER ( col_name , ) n COLUMNS DELIMITED BY char ENVELOPE NONE

key_constraint

PRIMARY KEY ( col_name , ) NOT ENFORCED

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.
FILE path The absolute path to the file you want to use as the source.
COMPRESSION algorithm The compression algorithm used with this file.
WITH ( option_list ) Options affecting source creation. For more detail, see WITH options.
HEADER Treat the first line of the CSV file as a header. See CSV format details.
HEADER (name_list) Treat the first line of the CSV file as a header, validate that the columns in the file match the provided column list. See CSV format details.
n COLUMNS Format the source’s data as a CSV with n columns. See CSV format details.
DELIMITED BY char Delimit the CSV by char. ASCII comma by default (','). This must be an ASCII character; other Unicode code points are not supported.
ENVELOPE NONE (Default) Use an append-only envelope. This means that records will only be appended and cannot be updated or deleted.
PRIMARY KEY ( col_list ) NOT ENFORCED Declare a set of columns as a primary key. For more information, see Key constraint details.

WITH options

The following options are valid within the WITH clause.

Field Value type Description
tail boolean Continually check the file for new content.
timestamp_frequency_ms int Default: 1000. Sets the timestamping frequency in ms. Reflects how frequently the source advances its timestamp. This measure reflects how stale data in views will be. Lower values result in more-up-to-date views but may reduce throughput.

Details

File source details

path values must be the file’s absolute path, e.g.

CREATE SOURCE server_source FROM FILE '/Users/sean/server.log'...

Compression

CSV format details

Materialize uses the format method you specify to determine the number of columns to create in the source, as well as the columns' names.

Method Outcome
HEADER Materialize reads the first line of the file to determine:

• The number of columns in the file

• The name of each column

The first line of the file is not ingested as data.
HEADER (name_list) All of the same behaviors as bare HEADER with the additional features that:

• Header names from source objects will be validated to exactly match those specified in the name list.

• Specifying a column list allows using CSV format with sources that have headers but individual objects may not yet exist. Primarily this is intended for S3 sources.
n COLUMNS • Materialize treats the file as if it has n columns.

• Columns are named column1, column2columnN.

Note that:

Types

Materialize treats all columns in CSV sources as text. You can “type” this data using casts when creating views using this source, e.g.:

CREATE MATERIALIZED VIEW salaries AS
  SELECT (employee_id::int, salary::numeric(38, 2))
  FROM csv_employee_data;

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.

Key constraint details

Primary keys are automatically inferred for Kafka sources using Upsert or Debezium envelopes and Postgres sources.

For other source configurations, the key_constraint syntax allows to manually declare a set of columns as a primary key. This enables optimizations and constructs that rely on a key to be present when it cannot be inferred.

WARNING! Materialize will not enforce the constraint and will produce wrong results if it is not correct.

Example

Creating a source from a static CSV

CREATE SOURCE static_w_header
FROM FILE '[path to .csv]'
FORMAT CSV WITH HEADER;

This creates a source that…

Creating a source from a dynamic CSV

CREATE SOURCE dynamic_wo_header (col_foo, col_bar, col_baz)
FROM FILE '[path to .csv]'
WITH (tail = true)
FORMAT CSV WITH 3 COLUMNS;

This creates a source that…

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