THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Page History
| ID | IEP-54 | ||||||||
| Author | |||||||||
| Sponsor | |||||||||
| Created |
| ||||||||
| Status |
|
...
BinaryObject API should be reworked, as it will not represent actual serialized objects anymore. It should be replaced with something like BinaryRecord or DataRecord representing a record in a cache or table. Similarly Similar to the current binary objects, records will provide access to individual fields. A record can also be deserialized into a class with any subset of fields represented in the record.
Schema Definition API
There are several ways a schema can be defined. The initial entry point to the schema definition is SchemaBuilder java API:
TBD (see SchemaBuilders class for details)
The schema builder calls are transparently mapped to DDL statements so that all operations possible via a builder are also possible via DDL and vice versa.
Data restrictions
The Schema-first approach imposes certain natural requirements which are more strict than binary object serialization format:
- The column type must be of one of a predefined set of available 'primitives' (including Strings, UUIDs, date & time values)
- Arbitrary nested objects and collections are not allowed as column values. Nested POJOs should either be inlined into a schema or stored as BLOBs
- Date & time values should be compressed with preserving natural order and decompression should be a trivial operation (like applying bitmask).
The suggested list of supported built-in data types is listed in the table below:
| Type | Size | Description |
|---|---|---|
| Bitmask(n) | ⌈n/8⌉ bytes | A fixed-length bitmask of n bits |
| Int8 | 1 byte | 1-byte signed integer |
| Uint8 | 1 byte | 1-byte unsigned integer |
| Int16 | 2 bytes | 2-byte signed integer |
| Uint16 | 2 bytes | 2-byte unsigned integer |
| Int32 | 4 bytes | 4-byte signed integer |
| Uint32 | 4 bytes | 4-byte unsigned integer |
| Int64 | 8 bytes | 8-byte signed integer |
| Uint64 | 8 bytes | 8-byte unsigned integer |
| Float | 4 bytes | 4-byte floating-point number |
| Double | 8 bytes | 8-byte floating-point number |
| Number([n]) | Variable | Variable-length number (optionally bound by n bytes in size) |
| Decimal | Variable | Variable-length floating-point number |
| UUID | 16 bytes | UUID |
| String | Variable | A string encoded with a given Charset |
| Date | 3 bytes | A timezone-free date encoded as a year (1 sign bit + 14 bits), month (4 bits), day (5 bits) |
| Time | 5 bytes | A timezone-free time encoded as padding (3 bits), hour (5 bits), minute (6 bits), second (6 bits), microseconds (20 bits) |
| Datetime | 8 bytes | A timezone-free datetime encoded as (date, time) |
| Timestamp | 10 bytes | Number of microseconds since Jan 1, 1970 00:00:00.000000 (with no timezone) |
| Binary | Variable | Variable-size byte array |
Data Layout
Given a set of user-defined columns, this set is then rearranged so that fixed-sized columns go first. This sorted set of columns is used to form a row. Row layout is as follows:
| Field | Size | Comments |
|---|---|---|
| Schema version | 2 bytes. | short number. The possible values are:
|
| Key columns hash | 4 bytes | |
| Key chunk: | ||
| Key chunk size | 4 bytes | |
| Flags | 1 byte | |
| Variable-length columns offsets table size | 0-2 bytes |
|
| Variable-length columns offsets table | Variable (number of non-null varlen columns * <format_size>) | <format_size> - depends on the Flags field. See the table below |
| Fix-sized columns values | Variable | |
| Variable-length columns values | Variable | |
| Value chunk: | ||
| Value chunk size | 4 bytes | |
| Flags | 1 byte | |
| Null-map | (number of columns / 8 ) or 0 bytes | Zero size if and only if schema has no nullable columns |
| Variable-length columns offsets table size | 2 or 0 bytes |
|
| Variable-length columns offsets table | Variable (number of non-null varlen columns * <format_size>) | <format_size> - depends on the Flags field. See the table below |
| Fix-sized columns values | Variable | |
| Variable-length columns values | Variable |
For the small rows, the metadata sizes may introduce a very noticeable overhead, so it looks reasonable to write them in a more compact way using different techniques.
- VarInt - variable size integer for sizes
- different VarTable formats with byte/short/int offsets
- skip writing VarTable and/or Null-map if possible.
The flags field is used to detect the format. We propose 3 formats for a vartable: tiny, medium, and large with offset fields sizes of byte, short, and int respectively.
Vartable length field is the size of byte for tiny format and the size of short for others.
Vertable length is calculated as: <count_of _not_null_varlen_fields> - 1. The offset for the first varlen field is not stored at the table. It is calculated as the begin of the varlen values block.
IMPORTANT: having multiple formats MUST guarantee the key (as well as value) chunk will be always written in a single possible way to allow comparing chunks of rows of the same version as just byte arrays.
The flags field is a bitmask with each bit treated as a flag, with the following flags available (from flag 0 being the LSB to flag 7 being MSB):
| Flags Bits | Description |
|---|---|
| 0, 1 | VarTable formats:
|
| 2-7 | Reserverd |
Risks and Assumptions
n/a
Tickets
| Jira | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
Discussion Links
Reference Links
n/a
...
n/a
Overview
Content Tools
Apps