Loading NDJSON File into Databend

What is NDJSON?

NDJSON is built on top of JSON, and it is a strict subset of JSON. Each line must contain a separate, self-contained valid JSON object.

The following example shows a NDJSON file with two JSON objects:

{"title":"Title_0","author":"Author_0"}
{"title":"Title_1","author":"Author_1"}

Loading NDJSON File

The common syntax for loading NDJSON file is as follows:

COPY INTO [<database>.]<table_name>
FROM { userStage | internalStage | externalStage | externalLocation }
[ PATTERN = '<regex_pattern>' ]
[ FILE_FORMAT = (
    TYPE = NDJSON,
    COMPRESSION = AUTO
) ]

More details about the syntax can be found in COPY INTO table.

Tutorial: Loading Data from NDJSON Files

Step 1. Create an Internal Stage

Create an internal stage to store the NDJSON files.

CREATE STAGE my_ndjson_stage;

Step 2. Create NDJSON files

Generate a NDJSON file using these SQL statements:

COPY INTO @my_ndjson_stage
FROM (
    SELECT
        'Title_' || CAST(number AS VARCHAR) AS title,
        'Author_' || CAST(number AS VARCHAR) AS author
    FROM numbers(100000)
)
    FILE_FORMAT = (TYPE = NDJSON)
;

Verify the creation of the NDJSON file:

LIST @my_ndjson_stage;

Result:

┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│                              name                              │   size  │                 md5                │         last_modified         │      creator     │
├────────────────────────────────────────────────────────────────┼─────────┼────────────────────────────────────┼───────────────────────────────┼──────────────────┤
│ data_b3d94fad-3052-42e4-b090-26409e88c7b9_0000_00000000.ndjson │ 4777780 │ "d1cc98fefc3e3aa0649cade880d754aa" │ 2023-12-26 12:15:59.000 +0000 │ NULL             │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

Step 3: Create Target Table

CREATE TABLE books
(
    title VARCHAR,
    author VARCHAR
);

Step 4. Copying Directly from NDJSON

To directly copy data into your table from NDJSON files, use the following SQL command:

COPY INTO books
FROM @my_ndjson_stage
PATTERN = '.*[.]ndjson'
FILE_FORMAT = (
    TYPE = NDJSON
);

Result:

┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│                              File                              │ Rows_loaded │ Errors_seen │    First_error   │ First_error_line │
├────────────────────────────────────────────────────────────────┼─────────────┼─────────────┼──────────────────┼──────────────────┤
│ data_b3d94fad-3052-42e4-b090-26409e88c7b9_0000_00000000.ndjson │      100000 │           0 │ NULL             │             NULL │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

Step 4 (Option). Using SELECT to Copy Data

For more control, like transforming data while copying, use the SELECT statement. Learn more at SELECT from NDJSON.

COPY INTO books(title, author)
FROM (
    SELECT $1:title, $1:author
    FROM @my_ndjson_stage
)
PATTERN = '.*[.]ndjson'
FILE_FORMAT = (
    TYPE = NDJSON
);