Question

我正在使用cassandra 2.x版本，并且要求将一行插入/更新到多个表。所有表都有不同的主键。如何将多个分配添加到更新，并将多个表名添加到QueryBuilder。使用datastax驱动程序。任何指针都会有所帮助。

Answer 1

其他人在Google群组中询问了how to batch update multiple tables。他们referred to a C# driver example多表更新。该原则适用于Java，我从cassandra java driver复制了相关的BatchStatement方法。

以下Java驱动程序引用的相关代码：

/**
     * Adds a new statement to this batch.
     * <p/>
     * Note that {@code statement} can be any {@code Statement}. It is allowed to mix
     * {@code RegularStatement} and {@code BoundStatement} in the same
     * {@code BatchStatement} in particular. Adding another {@code BatchStatement}
     * is also allowed for convenience and is equivalent to adding all the {@code Statement}
     * contained in that other {@code BatchStatement}.
     * <p/>
     * When adding a {@code BoundStatement}, all of its values must be set, otherwise an
     * {@code IllegalStateException} will be thrown when submitting the batch statement.
     * See {@link BoundStatement} for more details, in particular how to handle {@code null}
     * values.
     * <p/>
     * Please note that the options of the added Statement (all those defined directly by the
     * {@link Statement} class: consistency level, fetch size, tracing, ...) will be ignored
     * for the purpose of the execution of the Batch. Instead, the options used are the one
     * of this {@code BatchStatement} object.
     *
     * @param statement the new statement to add.
     * @return this batch statement.
     * @throws IllegalStateException if adding the new statement means that this
     *                               {@code BatchStatement} has more than 65536 statements (since this is the maximum number
     *                               of statements for a BatchStatement allowed by the underlying protocol).
     */
    public BatchStatement add(Statement statement) {

        // We handle BatchStatement here (rather than in getIdAndValues) as it make it slightly
        // easier to avoid endless loop if the use mistakenly pass a batch that depends on this
        // object (or this directly).
        if (statement instanceof BatchStatement) {
            for (Statement subStatements : ((BatchStatement) statement).statements) {
                add(subStatements);
            }
        } else {
            if (statements.size() >= 0xFFFF)
                throw new IllegalStateException("Batch statement cannot contain more than " + 0xFFFF + " statements.");
            statements.add(statement);
        }
        return this;
    }

基本思想是为每个表更新创建一个变量，并将每个变量添加到BatchStatement函数。

更新Cassandra中多个表中的行

1 个答案: