Database Reference
In-Depth Information
Extract of Sales Data
Address or Rowid
00001BFE.0012.0111
00001BFE.0013.0114
00001BFF.0012.0115
00001BFF.0012.0138
00001BFF.0012.0145
00001BFF.0012.0157
00001BFF.0014.0165
Date
15-Nov-00
15-Nov-00
16-Nov-00
16-Nov-00
17-Nov-00
17-Nov-00
17-Nov-00
Product
Dishwasher
Dryer
Dishwasher
Washer
Washer
Dryer
Washer
Color
White
Almond
Almond
Black
White
White
Almond
Region
East
West
West
North
South
East
South
Sale ($)
300
450
350
550
500
400
575
Bitmapped Index for Product Column
Ordered bits:
Washer, Dryer, Dishwasher
Bitmapped Index for Color Column
Ordered bits:
White, Almond, Black
Address or Rowid
00001BFE.0012.0111
00001BFE.0013.0114
00001BFF.0012.0115
00001BFF.0012.0138
00001BFF.0012.0145
00001BFF.0012.0157
00001BFF.0014.0165
Bitmap
001
010
001
100
100
010
100
Address or Rowid
00001BFE.0012.0111
00001BFE.0013.0114
00001BFF.0012.0115
00001BFF.0012.0138
00001BFF.0012.0145
00001BFF.0012.0157
00001BFF.0014.0165
Bitmap
100
010
010
001
100
100
010
Bitmapped Index for Region Column
Ordered bits: East, West, North, South
Address or Rowid
00001BFE.0012.0111
00001BFE.0013.0114
00001BFF.0012.0115
00001BFF.0012.0138
00001BFF.0012.0145
00001BFF.0012.0157
00001BFF.0014.0165
Bitmap
1000
0100
0100
0010
0001
1000
0001
Figure 12-17
Bitmapped indexes.
First or
Fourth Bit
=
1
First Bit
1
=
Second Bit
=
1
Product
001
010
001
100
100
010
100
Color
100
010
010
001
100
100
010
Region
1000
0100
0100
0010
0001
1000
0001
Address or Rowid
00001BFE.0012.0111
00001BFE.0013.0114
00001BFF.0012.0115
00001BFF.0012.0138
00001BFF.0012.0145
00001BFF.0012.0157
00001BFF.0014.0165
and
an
d
This row satisfies the query
Figure 12-18
Data retrieval with bitmapped indexes.
OTHER PERFORMANCE CONSIDERATIONS
Indexing is by far the widely used and most effective method for performance
improvement in a database system. In addition to the primary indexes automati-
cally created by the DBMS, the database administrator can create secondary indexes
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