> PG re-optmizes every query over and over unless you manually do a prepared statement and that only last for the session its prepared on.
But you really should using at least query builder that does the prepared statement thing under the hood, and also because writing dynamic queries with string concatenation sucks.
Parameterized sql is a good thing regardless of plan caching, but it also helps with systems that do plan caching.
That the client must explicitly prepare the statement and the preparation is tied to the connection is pretty clunky and still means the statement must be replanned for each separate connection.
Also since it is assumed by the devs of PG that prepared statements are not the norm they seem to avoid making the optimizer take its time and shoot for a fast optimizer rather than the fastest query.
DB's like MSSQL and Oracle concern themselves much less with how long it takes to optimize since repetitive queries will all use the same plan automatically it also allows interesting features like saving and loading plans from different systems and freezing them so they don't all the sudden go bad in production, but those systems also supports hints unlike PG.
But you really should using at least query builder that does the prepared statement thing under the hood, and also because writing dynamic queries with string concatenation sucks.