[FIX] expression: auto_join now uses LEFT JOIN

This fixes some cases where search results are actually missing.  For
instance, searching with a domain like

    ['|', ('parent_id.name', '=', 'foo'), ('name', 'like', 'foo')]

where `parent_id` is auto-joined, misses results where `parent_id` is
NULL, because the actual query makes cartesian products for auto-joins:

    SELECT "res_partner".id
    FROM "res_partner", "res_partner" AS "res_partner__parent_id"
    WHERE ("res_partner"."parent_id" = "res_partner__parent_id"."id")
    AND ("res_partner__parent_id"."name" = 'foo' OR "res_partner"."name" == 'foo')

Using LEFT JOIN instead of cartesian product above, the query includes
all results where `parent_id` is NULL:

    SELECT "res_partner".id
    FROM "res_partner"
    LEFT JOIN "res_partner" AS "res_partner__parent_id" ON
        ("res_partner"."parent_id" = "res_partner__parent_id"."id")
    WHERE ("res_partner__parent_id"."name" = 'foo' OR "res_partner"."name" == 'foo')

0 files changed, 0 insertions, 0 deletions