COUNT(DISTINCT *) is accepted and returns 1 for any number of rows #2758

COUNT(DISTINCT *) is accepted and returns 1. SQLite rejects it as a syntax error. Seen in the sqllogictest run (evidence/slt_lang_aggfunc.test), reproduced on develop (06211a0):

alasql('CREATE TABLE t1 (x INTEGER, y STRING)');
alasql("INSERT INTO t1 VALUES (1, 'true'), (0, 'false'), (NULL, 'NULL')");
alasql('SELECT COUNT(DISTINCT *) AS n FROM t1');   // [{n: 1}] for three different rows

Fix (4.x)

Count the distinct rows: 3 here. The answer is wrong today, so counting distinct rows does not break anyone.

Not changed

COUNT(DISTINCT *) stays accepted. Making it a syntax error, as SQLite does, would break code that runs it today; at most it belongs in the sqlite dialect, and is not tracked separately.