They may be useful in some cases, I just wanted to point out that in the particular case you gave they do not. See http://dba.stackexchange.com/questions/27481/is-a-composite-index-also-good-for-queries-on-the-first-field and http://dba.stackexchange.com/questions/6115/working-of-indexes-in-postgresql The scheduler will use the composite index for the first column and it will be as efficient as having an extra index only on this column. This allows to create less indexes and save some space :) Regarding the reverse, I agree it should not be a rule, but IMHO in 90-95% of the case it should be set. Even on small tables, where the cost of adding the index is minimal. For active / company, I think they are not often used since those are not very discriminative columns. Usually there is only one company, and almost all records are active...
|2016-07-29 11:41:06||jcavallo||set||messageid: <firstname.lastname@example.org>|
|2016-07-29 11:41:06||jcavallo||set||recipients: + ced, albertca, pokoli|
|2016-07-29 11:41:06||jcavallo||link||issue5757 messages|
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