Очень интересная фича в новой версии:
Статья
Glenn Paulley
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Determining error
In SQL Anywhere 12, the server monitors the amount of estimation error with each predicate in every search condition executed during query processing. The difference between actual and estimated selectivities is slightly biased against errors with small selectivities to avoid needless corrections. With this adjusted error, the server computes an error metric for each column histogram based on the number of predicates over that column and the amount of error. This metric is biased towards predicates that encounter significant differences between estimated and actual values, involving step functions when the error is between 20 and 35%, and another step when the error is greater than 35%. If this computed metric is greater than a threshold value, and the server has encountered more than 20 predicates involving that column, then the column histogram is considered a candidate for repair.
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