BUG: SQL-SELECT Performance Slower in 2.5x & 2.6 Than in 2.0

• Microsoft FoxPro for MS-DOS, versions 2.5, 2.5a, 2.5b, 2.6

SYMPTOMS

An SQL-SELECT statement runs much more slowly in FoxPro versions 2.5, 2.5a, 2.5b, and 2.6 for MS-DOS than it does in FoxPro 2.0 for MS-DOS.

CAUSE

Not all SELECT statements will exhibit this behavior. The conditions found to reproduce this type of situation include the following:

• The original data must be at least 70 MB in size.
• At least one of the conditions of the SELECT statement must produce >10,000 records. (The final result set may be small, but the result set of at least one of the intermediate conditions must be >10,000 records.)

RESOLUTION

To work around this problem, split the SELECT statement into at least two parts. Make sure that the initial SELECT condition is the one that narrows down the results the most. In this way, you will be working with a smaller result set that can then be narrowed down even further in subsequent SELECT statements. The performance of the SELECT statements will improve significantly.

STATUS

Microsoft has confirmed this to be a problem in FoxPro versions 2.5, 2.5a, 2.5b, 2.6 for MS-DOS. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.