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However for fast random access to individual tuple fields the general tuple structure depends only on the schema size. No other metadata is needed to find the required field. But one needs to learn the field data type from the schema when it is required to interpret the field as a value.

Tuple

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Layout

A binary tuple is kept as a sequence of fields contiguously going in memory one after another in the same order as they go in the tuple schema. The number of fields is defined by the schema too. Each field is a sequence of bytes that can be interpreted only after learning the field type in the schema.

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To represent NULL values a tuple may contain a nullmap. Nullmap is skipped if there are no actual NULL values in a given tuple.

To be more precise the layout of a tuple looks like this:

1. Header;
2. Nullmap;
3. Offset table;
4. Value area.

Reference Links

1. IEP-54: Schema-first Approach

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