On 7th of April 2018, Teodor Sigaev committed patch: Indexes with INCLUDE columns and their support in B-tree This patch introduces INCLUDE clause to index definition. This clause specifies a list of columns which will be included as a non-key part in the ...

On 8th of October, Tom Lane committed patch: Support index-only scans using the visibility map to avoid heap fetches. When a btree index contains all columns required by the query, and the visibility map shows that all tuples on a target heap page ...