On 30th of March 2017, Tom Lane committed patch: Support \if ... \elif ... \else ... \endif in psql scripting. This patch adds nestable conditional blocks to psql. The control structure feature per se is complete, but the boolean expressions understood by \if ...

On 23th of January, Simon Riggs committed patch: ALTER [IF EXISTS] ... allows silent DDL if required, e.g. ALTER FOREIGN TABLE IF EXISTS foo RENAME TO bar Pavel Stehule

On 25th Robert Haas committed patch which adds first of 'CREATE IF NOT EXISTS' commands: Log Message: ----------- CREATE TABLE IF NOT EXISTS.   Reviewed by Bernd Helmle.

On 20th of November Tom Lane committed patch by Takahiro Itagaki which adds interesting functionality: Add a WHEN clause to CREATE TRIGGER, allowing a boolean expression to be checked to determine whether the trigger should be fired.   For BEFORE triggers this is mostly ...

On 205h of July Andrew Dunstan committed patch by Andres Freund : Log Message: ----------- DROP IF EXISTS for columns and constraints. Andres Freund.