DatumTypeToArrayElementEncodingType decides an encoding type to place in the array header given a datum type.

Decode decodes a value encoded by Encode.

DecodeUntaggedDatum is used to decode a Datum whose type is known, and which doesn't have a value tag (either due to it having been consumed already or not having one in the first place).

Encode encodes `val` using value encoding and appends it to `appendTo`, returning the new buffer.

EncodeWithScratch is similar to Encode, but requires a scratch buffer that is used as a temporary buffer for certain datum types (JSON, arrays, tuples).

MakeColumnIDDelta creates the ColumnIDDelta for the difference between the given columns in the same value.

MakeDecoder creates a Decoder for the given columns.

MarshalLegacy produces the value encoding of the given datum (constrained by the given column type) into a roachpb.Value, using the legacy version 1 encoding (see docs/tech-notes/encoding.md).

UnmarshalLegacy is the counterpart to MarshalLegacy.

NoColumnID is a sentinel used when we aren't encoding a specific column ID.

Decoder is a helper for decoding rows that contain multiple encoded values.

ColumnIDDelta is the difference between two descpb.ColumnIDs.