ORC

This guide covers ingesting data from ORC files into BLUE using FOREIGN TABLE.

Foreign Data Wrapper Prerequisites

Before proceeding, ensure the following Foreign Data Wrapper (FDW) prerequisites:

  • File Existence: Verify that the file you are ingesting data from exists at the specified path.

  • Path Accuracy: Confirm that all path elements are present and correctly spelled. Any inaccuracies may lead to data retrieval issues.

  • Bucket Access Permissions: Ensure that you have the necessary access permissions to the bucket from which you are ingesting data. Lack of permissions can hinder the data retrieval process.

  • Wildcard Accuracy: If using wildcards, double-check their spelling and configuration. Misconfigured wildcards may result in unintended data ingestion.

Prepare The Files

Prepare the source ORC files, with the following requirements:

BLUE type →

ORC source

BOOL

TINYINT

SMALLINT

INT

BIGINT

REAL

DOUBLE

TEXT [1]

DATE

DATETIME

boolean

Supported

Supported [2]

Supported [2]

Supported [2]

Supported [2]

tinyint

○ [3]

Supported

Supported

Supported

Supported

smallint

○ [3]

○ [4]

Supported

Supported

Supported

int

○ [3]

○ [4]

○ [4]

Supported

Supported

bigint

○ [3]

○ [4]

○ [4]

○ [4]

Supported

float

Supported

Supported

double

Supported

Supported

string / char / text

Supported

date

Supported

Supported

timestamp, timestamp with timezone

Supported

  • If an ORC file has an unsupported type like binary, list, map, and union, but the data is not referenced in the table (it does not appear in the SELECT query), the statement will succeed. If the column is referenced, an error will be thrown to the user, explaining that the type is not supported, but the column may be ommited. This can be worked around. See more information in the examples.

Footnotes

Figure Out The Table Structure

Prior to loading data, you will need to write out the table structure, so that it matches the file structure.

For example, to import the data from nba.orc, we will first look at the source table:

nba.orc

Name

Team

Number

Position

Age

Height

Weight

College

Salary

Avery Bradley

Boston Celtics

0

PG

25

44714

180

Texas

7730337

Jae Crowder

Boston Celtics

99

SF

25

44718

235

Marquette

6796117

John Holland

Boston Celtics

30

SG

27

44717

205

Boston University

R.J. Hunter

Boston Celtics

28

SG

22

44717

185

Georgia State

1148640

Jonas Jerebko

Boston Celtics

8

PF

29

44722

231

5000000

Amir Johnson

Boston Celtics

90

PF

29

44721

240

12000000

Jordan Mickey

Boston Celtics

55

PF

21

44720

235

LSU

1170960

Kelly Olynyk

Boston Celtics

41

C

25

36708

238

Gonzaga

2165160

Terry Rozier

Boston Celtics

12

PG

22

44714

190

Louisville

1824360

  • The file is stored on S3, at s3://sqream-demo-data/nba.orc.

We will make note of the file structure to create a matching CREATE FOREIGN TABLE statement.

CREATE FOREIGN TABLE ext_nba (
  Name TEXT,
  Team TEXT,
  Number BIGINT,
  Position TEXT,
  Age BIGINT,
  Height TEXT,
  Weight BIGINT,
  College TEXT,
  Salary FLOAT
)
WRAPPER
  orc_fdw
OPTIONS
  (LOCATION = 's3://sqream-docs/nba.orc');

Tip

Types in BLUE must match ORC types according to the table above.

If the column type isn’t supported, a possible workaround is to set it to any arbitrary type and then exclude it from subsequent queries.

Verify Table Contents

External tables do not verify file integrity or structure, so verify that the table definition matches up and contains the correct data.

SELECT * FROM ext_nba LIMIT 10;

Name          | Team           | Number | Position | Age | Height | Weight | College           | Salary
--------------+----------------+--------+----------+-----+--------+--------+-------------------+---------
Avery Bradley | Boston Celtics |      0 | PG       |  25 | 6-2    |    180 | Texas             |  7730337
Jae Crowder   | Boston Celtics |     99 | SF       |  25 | 6-6    |    235 | Marquette         |  6796117
John Holland  | Boston Celtics |     30 | SG       |  27 | 6-5    |    205 | Boston University |
R.J. Hunter   | Boston Celtics |     28 | SG       |  22 | 6-5    |    185 | Georgia State     |  1148640
Jonas Jerebko | Boston Celtics |      8 | PF       |  29 | 6-10   |    231 |                   |  5000000
Amir Johnson  | Boston Celtics |     90 | PF       |  29 | 6-9    |    240 |                   | 12000000
Jordan Mickey | Boston Celtics |     55 | PF       |  21 | 6-8    |    235 | LSU               |  1170960
Kelly Olynyk  | Boston Celtics |     41 | C        |  25 | 7-0    |    238 | Gonzaga           |  2165160
Terry Rozier  | Boston Celtics |     12 | PG       |  22 | 6-2    |    190 | Louisville        |  1824360
Marcus Smart  | Boston Celtics |     36 | PG       |  22 | 6-4    |    220 | Oklahoma State    |  3431040

If any errors show up at this stage, verify the structure of the ORC files and match them to the external table structure you created.

Working Around Unsupported Column Types

Suppose you only want to load some of the columns - for example, if one of the columns isn’t supported.

By ommitting unsupported columns from queries that access the EXTERNAL TABLE, they will never be called, and will not cause a “type mismatch” error.

For this example, assume that the Position column isn’t supported because of its type.

CREATE TABLE
  nba AS
SELECT
  Name,
  Team,
  Number,
  NULL as Position,
  Age,
  Height,
  Weight,
  College,
  Salary
FROM
  ext_nba;

-- Removed the unsupported Position column and substituted it with a default NULL value to preserve table structure.