In the course of my practical tuning work, I came across a category of queries that are very difficult to optimize. These are queries with independent and not very selective search criteria across two (or more) tables.
A typical example is an address search using a person's name and place of residence. This category of queries is characterized by a potentially high number of "throw-away" records. "Throw-away" refers to records that are read during the course of an execution plan albania telegram screening but do not contribute to the final result. "Throw-away" records cannot always be avoided.
In this article I will describe a patented technique to keep the effort at a reasonable level.
A joke that illustrates a principle:
Two men are sitting together on a train. One of them takes a banana, peels it, puts salt on it and throws it out the window. Then he takes the next banana and repeats the process. After the third banana, his counterpart can no longer suppress his curiosity and asks: "Why are you throwing all these bananas out the window?" - "Well," the other replies, "do you like salted bananas?"
What's funny about this joke? Well, if you don't want a banana, what's the point of peeling it and salting it first? Can we imagine doing something similar in real life? For example, in the execution plans of a database?