SQL function pushdown

[ArthurBesse]

I am trying to create a custom JDBC connector, and will appreciate any help for solving the following problem.

I have the following query:

SELECT COLUMN_1,COLUMN_2 FROM CATALOG_NAME.SCHEMA_NAME.TABLE_NAME WHERE LOWER(COLUMN_3) = 'a';

But when I execute this query my jdbc driver receives the following modified query

SELECT COLUMN_1,COLUMN_2,COLUMN_3 FROM CATALOG_NAME.SCHEMA_NAME.TABLE_NAME;

As you can see my driver don't receive where clause. This is not what I want. I need to pushdown it.

Query without LOWER works as expected

SELECT COLUMN_1,COLUMN_2 FROM CATALOG_NAME.SCHEMA_NAME.TABLE_NAME WHERE COLUMN_3 = 'A';

My JDBC driver receives

SELECT COLUMN_1,COLUMN_2 FROM CATALOG_NAME.SCHEMA_NAME.TABLE_NAME WHERE COLUMN_3 = 'A';

This is part of my BaseJdbcClient implementation:

@Inject
public MyJdbcClient(
        BaseJdbcConfig config,
        ConnectionFactory connectionFactory,
        QueryBuilder queryBuilder,
        IdentifierMapping identifierMapping,
        RemoteQueryModifier remoteQueryModifier)
{
    super("\"", connectionFactory, queryBuilder, config.getJdbcTypesMappedToVarchar(), identifierMapping, remoteQueryModifier, true);

    this.connectorExpressionRewriter = JdbcConnectorExpressionRewriterBuilder.newBuilder()
            .addStandardRules(this::quoted)
            .add(new RewriteComparison(ImmutableSet.of(ComparisonOperator.EQUAL, ComparisonOperator.NOT_EQUAL)))
            .add(new RewriteIn())
            .withTypeClass("integer_type", ImmutableSet.of("tinyint", "smallint", "integer", "bigint"))
            .map("$add(left: integer_type, right: integer_type)").to("left + right")
            .map("$subtract(left: integer_type, right: integer_type)").to("left - right")
            .map("$multiply(left: integer_type, right: integer_type)").to("left * right")
            .map("$divide(left: integer_type, right: integer_type)").to("left / right")
            .map("$modulus(left: integer_type, right: integer_type)").to("left % right")
            .map("$negate(value: integer_type)").to("-value")
            .map("$like(value: varchar, pattern: varchar): boolean").to("value LIKE pattern")
            .map("$like(value: varchar, pattern: varchar, escape: varchar(1)): boolean").to("value LIKE pattern ESCAPE escape")
            .map("$not($is_null(value))").to("value IS NOT NULL")
            .map("$not(value: boolean)").to("NOT value")
            .map("$is_null(value)").to("value IS NULL")
            .map("$nullif(first, second)").to("NULLIF(first, second)")
            .build();
}

@Override
public Optional<ParameterizedExpression> convertPredicate(ConnectorSession session, ConnectorExpression expression, Map<String, ColumnHandle> assignments)
{
    return connectorExpressionRewriter.rewrite(session, expression, assignments);
}

Please advice which rule(s) I need to add to connectorExpressionRewriter in order to enable complex expressions (like LOWER(COLUMN_3) = 'a') pushdown.

P.s. I'm new to trino, so I appreciate your patience and willingness to help.