Null and default value Compression (V8 GA) : Compression for null, zero length data in variable length columns and system default value.

null值和缺省值压缩(V 8 GA)：对变长列中的零长度空数据和系统缺省值进行压缩。

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Without value compression, NULL values are stored with the data type inherent fixed size, which is typically larger than the three bytes.

如果不使用值压缩，则null值以数据类型固有的固定大小存储，这通常大于3个字节。

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NULL values are stored with only three bytes, if value compression is active. You can expect space savings especially for numeric values.

如果激活值压缩，则null值的存储只需3个字节。

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