Bitmap index concept: is it defined as an index on columns from two or more tables sharing the same value domain, or is that description incorrect?

Introduction / Context:
This question checks whether you can distinguish a standard bitmap index from related concepts such as a bitmap join index. Bitmap indexes are common in analytic workloads for low-cardinality columns.

Given Data / Assumptions:

• A bitmap index stores a bitmap for each distinct value of a column, indicating row positions where the value occurs.
• They are typically built on one table's column, enabling fast boolean combinations.
• A bitmap join index exists in some products and precomputes a join condition, but that is different from the basic definition.

Concept / Approach:
The prompt’s wording (“columns from two or more tables”) corresponds more to a join index, not to the general definition of a bitmap index. Therefore the statement is invalid.

Step-by-Step Solution:
Recall: bitmap index = value-to-bitmap mapping for a column in a table.Note: boolean operations on bitmaps accelerate multi-predicate filters.Contrast: bitmap join index pre-joins tables — a specialized feature.Conclude the given description does not match a standard bitmap index.

Verification / Alternative check:
Vendor docs show separate entries for “bitmap index” and “bitmap join index,” reinforcing the distinction.

Why Other Options Are Wrong:
Composite keys, foreign-key focus, or columnar storage do not redefine the basic bitmap index concept.

Common Pitfalls:
Equating all bitmap-based optimizations with the term “bitmap index.”

Final Answer:
Invalid — bitmap indexes map distinct values to bitmaps in a single table