[PG] PreparedQuery results in `ambiguous_parameter` error (42P08)

Version

4.2.1

Context

I encountered this error while refactoring a query to avoid unnecessary updates (similar to this StackOverflow post):

-- Before (works)
UPDATE repository
SET name = $2, description = $3
WHERE id = $1;

-- After (doesn't work)
UPDATE repository
SET name = $2, description = $3
WHERE id = $1 AND (repository.*) IS DISTINCT FROM ($1, $2, $3);

Running this query with PgPool.preparedQuery(...).execute(Tuple.of(...)) results in the following error:

2021-12-09 10:39:14,228 ERROR [com.example] (main @coroutine#2) CON: io.vertx.pgclient.PgException: ERROR: could not determine data type of parameter $2 (42P08)
	at io.vertx.pgclient.impl.codec.ErrorResponse.toException(ErrorResponse.java:31)
	at io.vertx.pgclient.impl.codec.PrepareStatementCommandCodec.handleErrorResponse(PrepareStatementCommandCodec.java:90)
	at io.vertx.pgclient.impl.codec.PgDecoder.decodeError(PgDecoder.java:246)
	at io.vertx.pgclient.impl.codec.PgDecoder.decodeMessage(PgDecoder.java:132)
	at io.vertx.pgclient.impl.codec.PgDecoder.channelRead(PgDecoder.java:112)

This is presumably because the client creates a prepared statement without explicit data types and Postgres tries to infer the type “…from the context in which the parameter is first referenced”, which I believe is actually in WHERE (ambiguous) and not in SET.

Expected

Ideally it would be possible to either create a prepared statement with explicit data types from a tuple (PrepareStatementCommand and PrepareStatementCommandCodec) so the statement is created as:

-PREPARE foo AS
+PREPARE foo (bigint, text, text) AS
UPDATE repository
SET name = $2, description = $3
WHERE id = $1 AND (repository.*) IS DISTINCT FROM ($1, $2, $3);

Perhaps 42P08 should be added to the list of indeterminate error codes as well.

Extra

As discussed in previous issues (#699 and #851), not defining explicit data types is an explicit choice:

We do not provide the parameters because some queries might use a different parameter types at execution time and that would result in a cast error in PG (e.g using a function that take any parameter as input, if you bind it with integer, then it will fail for a string).

[vietj]

@rgmz 4.2.2 will be released this week as soon as Netty 4.1.72.Final is released

[vietj]

it seems also one solution is to force the type in the query, e.g

UPDATE repository
SET name = $2::varchar, description = $3::varchar
WHERE id = $1::varchar AND (repository.*) IS DISTINCT FROM ($1::varchar, $2::varchar, $3::varchar);