PostgreSQL - max number of parameters in "IN" clause?

In Postgres, you can specify an IN clause, like this:

SELECT * FROM user WHERE id IN (1000, 1001, 1002)

Does anyone know what's the maximum number of parameters you can pass into IN?

Solution 1:

According to the source code located here, starting at line 850, PostgreSQL doesn't explicitly limit the number of arguments.

The following is a code comment from line 870:

/*
 * We try to generate a ScalarArrayOpExpr from IN/NOT IN, but this is only
 * possible if the inputs are all scalars (no RowExprs) and there is a
 * suitable array type available.  If not, we fall back to a boolean
 * condition tree with multiple copies of the lefthand expression.
 * Also, any IN-list items that contain Vars are handled as separate
 * boolean conditions, because that gives the planner more scope for
 * optimization on such clauses.
 *
 * First step: transform all the inputs, and detect whether any are
 * RowExprs or contain Vars.
 */

Solution 2:

This is not really an answer to the present question, however it might help others too.

At least I can tell there is a technical limit of 32767 values (=Short.MAX_VALUE) passable to the PostgreSQL backend, using Posgresql's JDBC driver 9.1.

This is a test of "delete from x where id in (... 100k values...)" with the postgresql jdbc driver:

Caused by: java.io.IOException: Tried to send an out-of-range integer as a 2-byte value: 100000
    at org.postgresql.core.PGStream.SendInteger2(PGStream.java:201)