Autovacuum analyze can't find C based function

Thomas Butz <tbutz@optitool.de> writes:

While installing Nominatim(OSM geocoding service) I stumbled upon this issue: https://github.com/openstreetmap/Nominatim/issues/1097#issue-341799919
The function "transliteration" has been properly created during the installation processes according to the following template:
https://github.com/openstreetmap/Nominatim/blob/v3.1.0/sql/functions.sql#L25

The strange thing is that i'm able to execute the function while background analyzation of the table "placex" repeatedly fails with the following error:

2018-07-17 06:59:35.908 UTC [30641] ERROR: function transliteration(text) does not exist at character 23

In recent PG releases, autovacuum executes stuff under a restrictive
search_path setting (just pg_catalog, in fact). So you need to do
something explicit to reference stuff in other schemas; either schema
qualify the name, or add a "SET search_path" clause to the function
definition. This is good practice anyway: what you're seeing is that this
function fails with any search_path other than the one you use by default.

regards, tom lane

Tom Lane <tgl@sss.pgh.pa.us> writes:

In recent PG releases, autovacuum executes stuff under a restrictive
search_path setting (just pg_catalog, in fact).

This should probably be added to section 24.1. of the documentation. At least i couldn't find it elsewhere.

So you need to do something explicit to reference stuff in other schemas; either schema
qualify the name

That solved my problem. Now the autovacuum daemon is able to find the function.

or add a "SET search_path" clause to the function
definition.

Could you elaborate a bit more on this? It seems like this would only limit/change which objects should be accessed
within the function as described by the CREATE FUNCTION documentation. The function itself wouldn't still be picked
up by the autovacuum daemon or am i missing something?

This is good practice anyway: what you're seeing is that this
function fails with any search_path other than the one you use by default.

regards, tom lane

--
Best regards

Thomas Butz

On Thu, Jul 19, 2018 at 10:29:27AM +0200, Thomas Butz wrote:

Tom Lane <tgl@sss.pgh.pa.us> writes:

In recent PG releases, autovacuum executes stuff under a restrictive
search_path setting (just pg_catalog, in fact).

This should probably be added to section 24.1. of the documentation. At least i couldn't find it elsewhere.

That wouldn't be unreasonable, but I think it's too much detail for the
documentation. What I'd find more promising is to refine the HINT to react
when the function exists in a schema outside search_path. Perhaps it would
then say "HINT: No function matches the given name, but other schemas have
functions of that name. You might need to schema-qualify the function name."
(I don't plan to implement that myself.)

or add a "SET search_path" clause to the function
definition.

Could you elaborate a bit more on this? It seems like this would only limit/change which objects should be accessed
within the function as described by the CREATE FUNCTION documentation. The function itself wouldn't still be picked
up by the autovacuum daemon or am i missing something?

Based on the error you posted, you would add the "SET search_path" clause to
function public.make_standard_name(text). Autovacuum did find
public.make_standard_name(text), but it did not find the transliteration(text)
function called inside the body of public.make_standard_name(text).