Is bitmap index useful

In what kind of situations b开发者_JAVA技巧itmap indices will be useful.

Bitmap indexes are useful in a *read-mostly environment to support queries consisting of several filters that combined provides *high selectivity when each individual filter would have *low selectivity.

• *Read-mostly = Data is infrequently updated
• *High selectivity = returns few rows
• *Low selectivity = returns lot of rows