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The following page has been changed by stack: http://wiki.apache.org/lucene-hadoop/Hbase/HbaseArchitecture The comment on the change is: Sync doc w/ code: Add 'family name' delimiter to all column names, etc. ------------------------------------------------------------------------------ may not have a value for a particular row key (sparse). The following example is a slightly modified form of the one on page 2 of the [http://labs.google.com/papers/bigtable.html Bigtable Paper]. [[Anchor(datamodelexample)]] - ||<:> '''Row Key''' ||<:> '''Time Stamp''' ||<:> '''Column''' ''"contents:"'' ||||<:> '''Column''' ''"anchor:"'' ||<:> '''Column''' ''"mime"'' || + ||<:> '''Row Key''' ||<:> '''Time Stamp''' ||<:> '''Column''' ''"contents:"'' ||||<:> '''Column''' ''"anchor:"'' ||<:> '''Column''' ''"mime:"'' || ||<^|5> "com.cnn.www" ||<:> t9 || ||<)> "anchor:cnnsi.com" ||<:> "CNN" || || ||<:> t8 || ||<)> "anchor:my.look.ca" ||<:> "CNN.com" || || ||<:> t6 ||<:> "<html>..." || || ||<:> "text/html" || @@ -105, +105 @@ It is important to note in the diagram above that the empty cells shown in the conceptual view are not stored. Thus a request for the - value of the ''"contents"'' column at time stamp ''t8'' would return + value of the ''"contents:"'' column at time stamp ''t8'' would return - a null value. Similarly, a request for an ''"anchor"'' value at time + a null value. Similarly, a request for an ''"anchor:"'' value at time stamp ''t9'' for "my.look.ca" would return a null value. However, if no timestamp is supplied, the most recent value for a particular column would be returned and would also be the first one found since time stamps are stored in descending order. Consequently - the value returned for ''"contents"'' if no time stamp is supplied is + the value returned for ''"contents:"'' if no time stamp is supplied is - the value for ''t6'' and the value for an ''"anchor"'' for + the value for ''t6'' and the value for an ''"anchor:"'' for "my.look.ca" if no time stamp is supplied is the value for time stamp ''t8''. === Example === - To show how data is stored on disk, consider the folloing example: + To show how data is stored on disk, consider the following example: A program writes rows "row[0-9]", column "anchor:foo"; then writes rows "row[0-9]"; column "anchor:bar"; and finally writes rows @@ -299, +299 @@ tablename + endkey + regionId. - You can see this identifier being constructed in + (You can see this identifier being constructed in the - HRegion.buildRegionName(). + HRegionInfo constructor.) [[Anchor(metadata)]] = META Table =