fix: Do not generate DISTINCT keyword in FILTER

sqlglot/generator.py

@@ -4323,6 +4323,13 @@ def arrayagg_sql(self, expression: exp.ArrayAgg) -> str:
                 parent_cond = parent.expression.this
                 parent_cond.replace(parent_cond.and_(expression.this.is_(exp.null()).not_()))
             else:
-                array_agg = f"{array_agg} FILTER(WHERE {self.sql(expression, 'this')} IS NOT NULL)"
+                # DISTINCT is already present in the agg function, do not propagate it to FILTER as well
+                this = expression.this
+                this_sql = (
+                    self.expressions(this)
+                    if isinstance(this, exp.Distinct)
+                    else self.sql(expression, "this")
+                )
+                array_agg = f"{array_agg} FILTER(WHERE {this_sql} IS NOT NULL)"
 
         return array_agg

tests/dialects/test_snowflake.py

@@ -755,6 +755,8 @@ def test_snowflake(self):
             write={
                 "spark": "SELECT COLLECT_LIST(DISTINCT a)",
                 "snowflake": "SELECT ARRAY_AGG(DISTINCT a)",
+                "duckdb": "SELECT ARRAY_AGG(DISTINCT a) FILTER(WHERE a IS NOT NULL)",
+                "presto": "SELECT ARRAY_AGG(DISTINCT a) FILTER(WHERE a IS NOT NULL)",
             },
         )
         self.validate_all(