How does ORC file work?
How does ORC file work?
File Structure An ORC file contains groups of row data called stripes, along with auxiliary information in a file footer. At the end of the file a postscript holds compression parameters and the size of the compressed footer. The default stripe size is 250 MB. Large stripe sizes enable large, efficient reads from HDFS.
How does ORC store data?
Actual data is stored in the ORC file in the form of rows of data that are called Stripes. Index data consists of min and max values for each column as well as the row positions within each column. ORC indexes help to locate the stripes based on the data required as well as row groups.
Are ORC files Splittable?
An ORC file consists of 1 or more “stripes”. These strips contain rows that are grouped together and can be read independent of each other. NEED TO VERIFY: ORC files are splittable at the “stripe”. This means that a large “ORC” file can be read in parallel across several containers.
Is ORC file compressed?
The ORC file format provides the following advantages: Efficient compression: Stored as columns and compressed, which leads to smaller disk reads. The columnar format is also ideal for vectorization optimizations in Tez.
Is parquet better than ORC?
ORC vs. PARQUET is more capable of storing nested data. ORC is more capable of Predicate Pushdown. ORC supports ACID properties. ORC is more compression efficient.
Is Parquet better than ORC?
Is ORC compressed by default?
The columnar format is also ideal for vectorization optimizations in Tez. Fast reads: ORC has a built-in index, min/max values, and other aggregates that cause entire stripes to be skipped during reads….Table 2.1. ORC Properties.
| Key | Default Setting | Notes |
|---|---|---|
| orc.compress | ZLIB | Compression type (NONE, ZLIB, SNAPPY). |
What is Avro and ORC?
The biggest difference between ORC, Avro, and Parquet is how the store the data. Parquet and ORC both store data in columns, while Avro stores data in a row-based format. While column-oriented stores like Parquet and ORC excel in some cases, in others a row-based storage mechanism like Avro might be the better choice.