The document provides a technical overview of ORC (Optimized Row Columnar) files, detailing their structure, serialization techniques for different data types, and compression methods. It discusses performance aspects such as query optimization, memory management, and vectorization. Additionally, it compares ORC with other file formats like RC file and Parquet, highlighting various features and advantages.

1. © Hortonworks Inc. 2012
ORC Files
June 2013
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Owen O’Malley
owen@hortonworks.com
@owen_omalley
owen@hortonworks.com

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Who Am I?
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History
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Remaining Challenges
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Requirements
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File Structure
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Stripe Structure
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File Layout
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File Footer
Postscript
Index Data
Row Data
Stripe Footer
256MBStripe
Index Data
Row Data
Stripe Footer
256MBStripe
Index Data
Row Data
Stripe Footer
256MBStripe
Column 1
Column 2
Column 7
Column 8
Column 3
Column 6
Column 4
Column 5
Column 1
Column 2
Column 7
Column 8
Column 3
Column 6
Column 4
Column 5
Stream 2.1
Stream 2.2
Stream 2.3
Stream 2.4

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Compression
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Integer Column Serialization
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String Column Serialization
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Hive Compound Types
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0
Struct
4
Struct
3
String
1
Int
2
Map
7
Time
5
String
6
Double

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Compound Type Serialization
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Generic Compression
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Column Projection
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How Do You Use ORC
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Managing Memory
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Pavan’s Trick
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Looking at ORC File Structures
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Looking at ORC File Structures
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TPC-DS File Sizes
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TPC-DS Query Performance
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Additional Details
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Current work
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Vectorization
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Vectorization Preliminary Results
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Future Work
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Thanks!
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Comparison
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RC File Trevni Parquet ORC File
Hive Type Model N N N Y
Separate complex columns N Y Y Y
Splits found quickly N Y Y Y
Default column group size 4MB 64MB* 64MB* 256MB
Files per a bucket 1 > 1 1* 1
Store min, max, sum, count N N N Y
Versioned metadata N Y Y Y
Run length data encoding N N Y Y
Store strings in dictionary N N N Y
Store row count N Y N Y
Skip compressed blocks N N N Y
Store internal indexes N N N Y