In a nutshell: - Puts are collected in memory (in a sorted data structure) - When the collected data reaches a certain size it is flushed to a new file (which is sorted) - Gets do a merge sort between the various files that have been created - to contain the number of files they are periodically compacted into fewer, larger files
So the data files (HFiles) are immutable once written, changes are batched in memory first. -- Lars ________________________________ From: "Pamecha, Abhishek" <apame...@x.com> To: "user@hbase.apache.org" <user@hbase.apache.org> Sent: Tuesday, August 21, 2012 4:00 PM Subject: HBase Put Hi I had a question on Hbase Put call. In the scenario, where data is inserted without any order to column qualifiers, how does Hbase maintain sortedness wrt column qualifiers in its store files/blocks? I checked the code base and I can see checks<https://github.com/apache/hbase/blob/trunk/hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileWriterV2.java#L319> being made for lexicographic insertions for Key value pairs. But I cant seem to find out how the key-offset is calculated in the first place? Also, given HDFS is by nature, append only, how do randomly ordered keys make their way to sorted order. Is it only during minor/major compactions, that this sortedness gets applied and that there is a small window during which data is not sorted? Thanks, Abhishek
