On 1/16/15 11:16 AM, Pavel Stehule wrote:
2015-01-16 17:57 GMT+01:00 Jim Nasby <jim.na...@bluetreble.com <mailto:jim.na...@bluetreble.com>>: On 1/16/15 3:39 AM, Pavel Stehule wrote: I am proposing a simple function, that returns a position of element in array. Yes please! FUNCTION array_position(anyarray, anyelement) RETURNS int That won't work on a multi-dimensional array. Ideally it needs to accept a slice or an element and return the specifier for the slice. It is question, what is a result - probably, there can be a multidimensional variant, where result will be a array array_position([1,2,3],2) --> 2 array_position([[1,2],[2,3],[3,4]], [2,3]) --> 2 /* 2nd parameter should to have N-1 dimension of first parameter */
The problem with that is you can't actually use '2' to get [2,3] back: select (array[[1,2,3],[4,5,6],[7,8,9]])[1] IS NULL; ?column? ---------- t (1 row) I think the bigger problem here is we need something better than slices for handling subsets of arrays. Even if the function returned [2:2] it's still going to behave differently than it will in the non-array case because you won't be getting the expected number of dimensions back. :(
array_position_md([1,2,3],2) --> [2] array_position_md([[1,2],[2,3],[3,4]], 2) --> [2,1] another question is how to solve more than one occurrence on one value - probably two sets of functions - first returns first occurrence of value, second returns set of occurrence
Gee, if only way had some way to return multiple elements of something... ;P In other words, I think all of these should actually return an array of positions. I think it's OK for someone that only cares about the first instance to just do [1]. -- Jim Nasby, Data Architect, Blue Treble Consulting Data in Trouble? Get it in Treble! http://BlueTreble.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
