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Utilities for debugging, profiling and code coverage measure for UDFs.

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package com.exasol.udfdebugging;

import java.io.StringReader;
import java.sql.*;

import jakarta.json.*;

/**
 * This class contains helper functions for testing virtual schema push down queries.
 */
public class PushDownTesting {

    /**
     * Get the push-down SQL query generated by a Virtual Schema adapter call.
     * 
     * @param statement SQL statement
     * @param query     query to a Virtual Schema table
     * @return generated push down query
     * @throws SQLException if execution fails
     */
    public static String getPushDownSql(final Statement statement, final String query) throws SQLException {
        try (final ResultSet pushDownSqlResult = statement
                .executeQuery("SELECT PUSHDOWN_SQL FROM (EXPLAIN VIRTUAL " + query + ");")) {
            pushDownSqlResult.next();
            return pushDownSqlResult.getString("PUSHDOWN_SQL");
        }
    }

    /**
     * Get the selection (where clause) that the Exasol database passed to the Virtual Schema adapter.
     * 
     * @param statement SQL statement
     * @param query     query to a Virtual Schema table
     * @return selection (where clause)
     * @throws SQLException if SQL statement fails
     */
    public static String getSelectionThatIsSentToTheAdapter(final Statement statement, final String query)
            throws SQLException {
        try (final ResultSet pushDownSqlResult = statement
                .executeQuery("SELECT PUSHDOWN_JSON FROM (EXPLAIN VIRTUAL " + query + ");")) {
            pushDownSqlResult.next();
            final String pushdownJson = pushDownSqlResult.getString("PUSHDOWN_JSON");
            try (final JsonReader reader = Json.createReader(new StringReader(pushdownJson))) {
                final JsonObject response = reader.readArray().get(2).asJsonObject();
                return response.getJsonObject("pushdownRequest").getString("filter_expr_string_for_debug", "");
            }
        }
    }
}