— part of check-in
on branch trunk
— Many code simplifications. Removing support for shared-cache mode, VACUUM,
multiplexor, test_stat, progress handler, etc.
The key for each row of a table is the defined PRIMARY KEY in the key
encoding. Or, if the table does not have a defined PRIMARY KEY, then
it has an implicit INTEGER PRIMARY KEY as the first column.
The content consists of all columns of the table, in order, in the data
encoding defined here. The PRIMARY KEY column or columns are repeated
in the data, due to the difficulty in decoding the key format.
The data consists of a header area followed by a content area. The data
begins with a single varint which is the size of the header area. The
initial varint itself is not considered part of the header. The header
is composed of one or two varints for each column in the table. The varints
determines the datatype and size of the value for that column:
3..10 (N-2)-byte signed integer
11..21 (N-9)-byte number (two varints: min 2, max 12 bytes)
22+3*K K-byte string
23+3*K K-byte inline blob
24+3*K K-byte typed blob, followed by a single varint type code
Strings can be either UTF8, UTF16le, or UTF16be. If the first byte of the
payload is 0x00, 0x01, or 0x02 then that byte is ignored and the remaining
bytes are UTF8, UTF16le, or UTF16be respectively. If the first byte is 0x03
or larger, then the entire string including the first byte is UTF8.
A "typed blob" is a sequence of bytes in an application-defined type.
The type is determined by a varint that immediately follows the initial
varint. Hence, a typed blob uses two varints in the header whereas all
other types use a single varint.
The content of a number is two varints. The first varint has a value
which is abs(e)*4 + (e<0)*2 + (m<0). The second varint is abs(m).
The maximum e is 999, which gives a max varint value of 3999 or 0xf906af, for
a maximum first varint size of 3. Values of e greater than 999 (used for
Inf and NaN) are represented as a -0. The second varint can be a full 9 bytes.
0.123 -> e=-3, m=123 -> 0e,7b (2 bytes)
3.14159 -> e=-5, m=314159 -> 16,fa04cb2f (5 bytes)
-1.2e+99 -> e=98, m=-12 -> f199,0c (3 bytes)
+Inf -> e=-0, m=1 -> 02,01 (2 bytes)
-Inf -> e=-0, m=-1 -> 03,01 (2 bytes)
NaN -> e=-0, m=0 -> 02,00 (2 bytes)
Initially, the followed typed blobs are defined:
0 external blob
1 big int