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by woodman
4011 days ago
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SQLite does this, autoindex[0]. "When no indices are available to aid the evaluation of a query, SQLite might create an automatic index that lasts only for the duration of a single SQL statement. Since the cost of constructing the automatic index is O(NlogN) (where N is the number of entries in the table) and the cost of doing a full table scan is only O(N), an automatic index will only be created if SQLite expects that the lookup will be run more than logN times during the course of the SQL statement." [0] http://www.sqlite.org/optoverview.html#autoindex |
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