Why does the “random concordances” function take much longer to match some phrases than others?
Ironically, the more frequent a phrase and the words in it are, the longer it takes to compile a random set of concordances. In addition, this feature takes advantage of a “fulltext” index, which improves efficiency by excluding “short” words (< 4 letters) and ones which occur in over half the sentences (e.g. a, and, the, is, are...). Finding these unindexed words takes longer than more salient words. To improve speed, queries consisting mainly or entirely of such short and frequent words are run against a randomized database: the sentences are in scrambled order, but matching proceeds in the same order for each new round of concordances. (Nevertheless, the "Re-Query" link finds any additional matches of your search text.) This pseudo-random approach usually provides satisfactory results in a fraction of the time required for a truly random search. You can tell which query method was used by the codes at the bottom right of the results page (ft 'fulltext index', rt 'randomized text', f
