T
Thomas Mercer-Hursh
Guest
But, the point is not that you need the single field indices to be used alone, but that you can use them in combination with other indices to create selections or sorts. Your main selections and sorts of course deserve their own indices, but big tables which are analyzed a lot have a pattern of having a wide array of ways in which they are sliced and diced. At the very least, the first thing you should do is to build up a database of every query, which indexes are currently used, which fields are used, and what order they are used in. i.e., the sort order. If you then find indices that are not used and which are not needed as constraints, e.g., uniqueness, then by all means get rid of them Likewise, if you find that every use of these three fields is the same fields and the same order, then you have a good argument for substituting an appropriate index, existing or new. But, my bet is that you will find the queries all over the map, not uniformly since many will be the same, but there will be different ones that are nevertheless important and which would perform much worse without those single field indices.
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