Linear hashing: Difference between revisions

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{{Citation | first1 = K. |last1 = Ramamohanarao | first2 = R. | last2 = Sacks-Davis |
title = Recursive linear hashing |
journal = ACM Transactions on DatabasesDatabase Systems|
volume=9 | number=3 |date=Sep 1984 | pages=369–391|doi = 10.1145/1270.1285 |s2cid = 18577730 |doi-access = free }}
</ref>
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Linear hashing algorithms may use only controlled splits or both controlled and uncontrolled splits.
 
'''Controlled splitting''' occurs if a split is performed whenever the [[load factor (computer science)|load factor]], which is monitored by the file, exceeds a predetermined threshold.<ref name="LMS" /> If the hash index uses controlled splitting, the buckets are allowed to overflow by using linked overflow blocks. When the ''load factor'' surpasses a set threshold, the ''split pointer's'' designated bucket is split. Instead of using the load factor, this threshold can also be expressed as an occupancy percentage, in which case, the maximum number of records in the hash index equals (occupancy percentage)*(max records per non-overflowed bucket)*(number of buckets).<ref name=":0">{{Cite book |lastlast1=Silberschatz |firstfirst1=Abraham |title=Database system concepts |last2=Korth |first2=Henry F. |last3=Sudarshan |first3=S. |date=2020 |publisher=McGraw-Hill Education |isbn=978-1-260-08450-4 |edition=Seventh |___location=New York, NY}}</ref>
 
An '''uncontrolled split''' occurs when a split is performed whenever a bucket overflows, in which case that bucket would be split into two separate buckets.