Hi all,
after discusion with Jim, I was created frist draft of proposal for
value encoding.
Pros: efectivity for numerical values including date and time
Cons: poor for strings (can be worst then current), can be solved by
apply RLE (not current) over final result.
It is designed as simple (there is space for improovement, but general
value distribution function should be know)
and easy to implement.
It is use data from record format to skip length storage where is posible.
Control byte= code:3bits + Value:5bits
Code Value Meaning
===== =======
0
0 NULL
1 Float Nan
2-31 Unused
1
0 Fixed Binary (length comes from record format)
1-31 Unused
2 Int5 - (-16~15) from value
3 Int13 +1byte
4 Int21 +2bytes
5 Int29 +3bytes
6 Int37 +4bytes
7 Int45 +5bytes
DataType in format structure:
INT - stored by absolute value, fixed binary for INT greater
than 2^45
VARCHAR - int (length) + bytes[lenght]
CHAR - VARCHAR + fill space
DATE - Value-'1.1.2016' stored as int (nuber of days)
TIME - Time - '12:00:00' PM (noon) and stored as INT (what is
requested precision?)
TIMESTAMP - as DATE followed by TIME
FLOAT - integer value stored as integer, else Fixed binary (4)
DOUBLE PRECISION - integer value stored as integer, else Fixed binary (8)
DECIMAL - Stored as INT
BLOBID - stored as integer
Record format:
uint32 tr_id
uint8 format
<data>
Any comments?
Slavek
--
Ing. Slavomir Skopalik
Executive Head
Elekt Labs s.r.o.
Collection and evaluation of data from machines and laboratories
by means of system MASA (http://www.elektlabs.cz/m2demo)
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