Databases Reference
In-Depth Information
String Page K
String M
String M+1
Type
Length
Te x t
End
Type
Length
String M+1
…
Te x t
End
String T
…
Type
Length
String T
…
Te x t
End
Page N
String Page K + 1
Record 1
String T
String T+1
Numeric Field
…
String Field
Null Bits
Type
Length
Te x t
End
Type
Length
Record 2
String T+1
…
Numeric Field
…
String Field
Null Bits
Te x t
End
String F
…
…
Type
Length
Record N
String F
Numeric Field
…
String Field
Null Bits
Te x t
End
…
…
FIGURE 20.2
Analysis Services stores text data in a data structure called a string store.
Compressed Store Structure
Analysis Services can store data in the data store in a compressed format. In that case, the
fields of the store typically use fewer bytes than the number of bytes required to store an
uncompressed value of a given data type. In reality, the amount of memory required is
measured in bits rather than bytes because the fields are packed together and the bits for
these fields are stored consecutively, disregarding byte alignment.
When Analysis Services creates a compressed store, it marks some fields of the records as
key fields and the other fields as data fields so that the record is divided in two parts: the
key part of the record (which contains key fields), and the data part of the record (which
contains data fields). Keys are separated from data in a compressed store to make building
of indexes more efficient.
Analysis Services analyzes the data to be stored in the compressed store and determines
whether it can compress a field and, if so, the ratio of compression it can achieve. Fields
Search WWH ::
Custom Search