Hash indexes

- [Instructor] The next type of index we'll discuss … is the hash index. … The basis of this kind of index is a function … called the hash function. … Hash functions take an arbitrary length data and map it … to a fixed-size value. … Hash functions are designed so that different inputs … produce different outputs. … Occasionally two different inputs will produce … the same output, but that's highly unlikely. … In general, even a slight change in input will produce … a different hash value. … The hash value that is created can vary in size … depending on which hash algorithm is used. … You will notice in this example, that similar … output strings can produce widely different hash values. … Adding a single letter or changing the case … of a letter is sufficient to lead to a new value. … Notice also that there's no order preserving operation … with hash functions. … Here are a few things to keep in mind about hash indexes. … They're only used for equality comparisons. … Hash values won't help if you want to filter …