On 10/7/2014 4:44 PM, Jonathan Vanasco wrote:
I had created a "unique index" on a mix of two columns to enforce a constraint
: (resource_type_id, lower(archive_pathname))
i've noticed that searches never use this. no matter what I query, even if
it's only the columns in the index. I'm seeing a 550ms sequential scan on
everything.
If I create an index only on the text field: lower(archive_pathname) , all the
queries use that and complete in 1.4ms
does anyone know why this happens ?
the index (resource_type_id, lower(archive_pathname)) should certainly
get used on queries like...
select <stuff> from table where resource_type_id = $1 and
lower(archive_pathname) = $2; the 2nd = could be > or < too.
It also should get used on queries with resource_type_id = $1, unless
thats not very selective (millions of records with just a few
resource_type_id values, for instance).
--
john r pierce 37N 122W
somewhere on the middle of the left coast
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