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Boolean Representation

A single byte containing 1   for the value of true. The and 0 for the value of false does not need any representation as it stored as a default zero-size field.

Corollary

If the number of fields is N and t is an array that stores a binary tuple we can find the answers for the following:Does the tuple contain a nullmap?

hasNullmap = t[0] & 0b100;

How many bytes are occupied by the nullmap?

nullmapBytes = hasNullmap ? (N + 7) / 8 : 0;

How many bytes are occupied by one offset table entry?

offsetEntryBytes = 1 << (t[0] & 0b11);

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What is offset of the value area?

valueBaseOffset = 1 + nullmapBytes + offsetTableBytes;

What is the whole tuple size?

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In order to build a tuple using minimum possible space it is required to learn two things:

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what is the total length of all non-null values

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. After that we can figure out the minimum possible size of the offset table entries.

Thus, generally speaking, building a binary tuple is a two-pass procedure. Sometimes it might be possible to turn this into a single pass (almost) by over-provisioning the allocated storage for the worst case and then fixing it up at the end.

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