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Small File
BibTeX
@MISC{Lavery_smallfile,
author = {Russell Lavery and Contractor For About-consulting and Chadds Ford and Why Learn Hashing},
title = {Small File},
year = {}
}
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Abstract
Hashing is one of the fastest table lookup techniques, not just in SAS®, but in any programming language. Figure 1 illustrates the concept of a table lookup and the speed advantage of SAS V9 Hashing over a format table lookup. If a programmer needs to select, from a large file, all subjects that are in a small file, hashing will likely save disk space and time. Hashing should be part of the tool kit of every programmer who deals with large files. Hashing is designed to allow a programmer to subset a large file, based on information in a small file (as is shown in figure 1). While that is the designed reason for SAS adding this new feature, hashing can also replace by merges, format lookups and IORC merges. A major benefit of hashing, is that it can perform a table lookup using two unsorted datasets. Sorting is a disk and CPU intensive process. The techniques described in the series of papers named the Animated Guide©: Speed Merges: have, as a common theme, the desire to not sort the data. This paper, on SAS V9.1 Hashing, is the fourth in the “speed merging ” series and recommends that V9.1 hashing be considered for general use because of its speed and ease of use.
Keyphrases
small file large file table lookup general use iorc merges common theme major benefit speed merges sa v9 disk space programming language sa v9 hashing speed advantage table lookup technique format lookup cpu intensive process animated guide designed reason tool kit new feature unsorted datasets format table lookup
