| | 2 | |
| | 3 | PostgreSQL 9.6 gets rid of most of pg_am columns[0]. In particular, amcanorder disappears and should be replaced with calls to pg_index_column_has_property(). PostgreSQL versions < 9.6 do not provide this method, hence we are forced to rely on a brittle query. |
| | 4 | |
| | 5 | Since only B-tree indexes support ordering[1], this is the only type of index to consider. This solution relies on the access method implementation[2] to determine whether ASC or DESC ordering is in use. |
| | 6 | |
| | 7 | Let's hope that a new view is added to information_schema[3] in the future. |
| | 8 | |
| | 9 | [0] https://www.postgresql.org/docs/9.6/static/release-9-6.html |
| | 10 | [1] https://www.postgresql.org/docs/current/static/indexes-ordering.html |
| | 11 | [2] https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/catalog/pg_index.h;h=ee97c5dec836ad82c5b75440fcba51d4c106fc33;hb=HEAD#l99 |
| | 12 | [3] http://stackoverflow.com/questions/18121103/how-to-get-the-index-column-orderasc-desc-nulls-first-from-postgresql#comment64529591_18128104 |