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205 lines
10 KiB
Markdown
205 lines
10 KiB
Markdown
## 8 Binlog
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InsertBinlog、DeleteBinlog、DDLBinlog
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Binlog is stored in a columnar storage format, every column in schema is stored in an individual file.
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Timestamp, schema, row id and primary key allocated by system are four special columns.
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Schema column records the DDL of the collection.
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## Event format
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Binlog file consists of 4 bytes magic number and a series of events. The first event must be descriptor event.
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### 8.1 Event format
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```
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+=====================================+=====================================================================+
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| event | Timestamp 0 : 8 | create timestamp |
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| header +----------------------------+---------------------------------------------------------------------+
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| | TypeCode 8 : 1 | event type code |
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| +----------------------------+---------------------------------------------------------------------+
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| | EventLength 9 : 4 | length of event, including header and data |
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| +----------------------------+---------------------------------------------------------------------+
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| | NextPosition 13 : 4 | offset of next event from the start of file |
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+=====================================+=====================================================================+
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| event | fixed part 17 : x | |
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| data +----------------------------+---------------------------------------------------------------------+
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| | variable part | |
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+=====================================+=====================================================================+
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```
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### 8.2 Descriptor Event format
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```
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+=====================================+=====================================================================+
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| event | Timestamp 0 : 8 | create timestamp |
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| header +----------------------------+---------------------------------------------------------------------+
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| | TypeCode 8 : 1 | event type code |
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| +----------------------------+---------------------------------------------------------------------+
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| | EventLength 9 : 4 | length of event, including header and data |
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| +----------------------------+---------------------------------------------------------------------+
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| | NextPosition 13 : 4 | offset of next event from the start of file |
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+=====================================+=====================================================================+
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| event | CollectionID 17 : 8 | collection id |
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| data +----------------------------+---------------------------------------------------------------------+
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| | PartitionID 25 : 8 | partition id (schema column does not need) |
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| +----------------------------+---------------------------------------------------------------------+
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| | SegmentID 33 : 8 | segment id (schema column does not need) |
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| +----------------------------+---------------------------------------------------------------------+
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| | FieldID 41 : 8 | field id (schema column does not need) |
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| +----------------------------+---------------------------------------------------------------------+
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| | StartTimestamp 49 : 8 | minimum timestamp allocated by master of all events in this file |
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| +----------------------------+---------------------------------------------------------------------+
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| | EndTimestamp 57 : 8 | maximum timestamp allocated by master of all events in this file |
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| +----------------------------+---------------------------------------------------------------------+
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| | PayloadDataType 65 : 4 | data type of payload |
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| +----------------------------+---------------------------------------------------------------------+
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| | ExtraLength 69 : 4 | length of extra information |
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| +----------------------------+---------------------------------------------------------------------+
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| | ExtraBytes 73 : n | extra information in json format |
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| +----------------------------+---------------------------------------------------------------------+
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| | PostHeaderLengths n : n | header lengths for all event types |
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+=====================================+=====================================================================|
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```
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`ExtraBytes` is in json format.
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`ExtraBytes` stores the extra information of the binlog file.
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In binlog file, we have stored many common fields in fixed part, such as `CollectionID`, `PartitionID` and etc.
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However, different binlog files have some other different information which differs from each other.
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So, `ExtraBytes` was designed to store these different information.
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For example, for index binlog file, we will store `indexID`, `indexBuildID`, `indexID` and other index-related
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information to `ExtraBytes`.
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In addition, `ExtraBytes` was also designed to extend binlog. Then we can add new features to binlog file without
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breaking the compatibility.
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For example, we can store the memory size of original content(before encode) to `ExtraBytes`.
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The key in `ExtraBytes` is `original_size`. For now, `original_size` is required, not optional.
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### 8.3 Type code
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```
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DESCRIPTOR_EVENT
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INSERT_EVENT
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DELETE_EVENT
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CREATE_COLLECTION_EVENT
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DROP_COLLECTION_EVENT
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CREATE_PARTITION_EVENT
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DROP_PARTITION_EVENT
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```
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DESCRIPTOR_EVENT must appear in all column files and always be the first event.
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INSERT_EVENT 可以出现在除 DDL binlog 文件外的其他列的 binlog
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DELETE_EVENT 只能用于 primary key 的 binlog 文件（目前只有按照 primary key 删除）
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CREATE_COLLECTION_EVENT、DROP_COLLECTION_EVENT、CREATE_PARTITION_EVENT、DROP_PARTITION_EVENT 只出现在 DDL binlog 文件
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### 8.4 Event data part
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```
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event data part
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INSERT_EVENT:
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+================================================+==========================================================+
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| event | fixed | StartTimestamp x : 8 | min timestamp in this event |
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| data | part +------------------------------+----------------------------------------------------------+
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| | | EndTimestamp x+8 : 8 | max timestamp in this event |
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| +--------+------------------------------+----------------------------------------------------------+
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| |variable| parquet payload | payload in parquet format |
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| |part | | |
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+================================================+==========================================================+
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other events are similar with INSERT_EVENT
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```
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### 8.5 Example
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Schema
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string | int | float(optional) | vector(512)
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Request:
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InsertRequest rows(1W)
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DeleteRequest pk=1
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DropPartition partitionTag="abc"
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insert binlogs:
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rowid, pk, ts, string, int, float, vector 6 files
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all events are INSERT_EVENT
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float column file contains some NULL value
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delete binlogs:
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pk, ts 2 files
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pk's events are DELETE_EVENT, ts's events are INSERT_EVENT
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DDL binlogs:
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ddl, ts
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ddl's event is DROP_PARTITION_EVENT, ts's event is INSERT_EVENT
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C++ interface
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```c++
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typedef void* CPayloadWriter
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typedef struct CBuffer {
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char* data;
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int length;
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} CBuffer
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typedef struct CStatus {
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int error_code;
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const char* error_msg;
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} CStatus
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// C++ interface
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// writer
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CPayloadWriter NewPayloadWriter(int columnType);
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CStatus AddBooleanToPayload(CPayloadWriter payloadWriter, bool *values, int length);
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CStatus AddInt8ToPayload(CPayloadWriter payloadWriter, int8_t *values, int length);
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CStatus AddInt16ToPayload(CPayloadWriter payloadWriter, int16_t *values, int length);
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CStatus AddInt32ToPayload(CPayloadWriter payloadWriter, int32_t *values, int length);
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CStatus AddInt64ToPayload(CPayloadWriter payloadWriter, int64_t *values, int length);
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CStatus AddFloatToPayload(CPayloadWriter payloadWriter, float *values, int length);
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CStatus AddDoubleToPayload(CPayloadWriter payloadWriter, double *values, int length);
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CStatus AddOneStringToPayload(CPayloadWriter payloadWriter, char *cstr, int str_size);
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CStatus AddBinaryVectorToPayload(CPayloadWriter payloadWriter, uint8_t *values, int dimension, int length);
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CStatus AddFloatVectorToPayload(CPayloadWriter payloadWriter, float *values, int dimension, int length);
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CStatus FinishPayloadWriter(CPayloadWriter payloadWriter);
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CBuffer GetPayloadBufferFromWriter(CPayloadWriter payloadWriter);
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int GetPayloadLengthFromWriter(CPayloadWriter payloadWriter);
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CStatus ReleasePayloadWriter(CPayloadWriter handler);
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// reader
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CPayloadReader NewPayloadReader(int columnType, uint8_t *buffer, int64_t buf_size);
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CStatus GetBoolFromPayload(CPayloadReader payloadReader, bool **values, int *length);
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CStatus GetInt8FromPayload(CPayloadReader payloadReader, int8_t **values, int *length);
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CStatus GetInt16FromPayload(CPayloadReader payloadReader, int16_t **values, int *length);
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CStatus GetInt32FromPayload(CPayloadReader payloadReader, int32_t **values, int *length);
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CStatus GetInt64FromPayload(CPayloadReader payloadReader, int64_t **values, int *length);
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CStatus GetFloatFromPayload(CPayloadReader payloadReader, float **values, int *length);
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CStatus GetDoubleFromPayload(CPayloadReader payloadReader, double **values, int *length);
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CStatus GetOneStringFromPayload(CPayloadReader payloadReader, int idx, char **cstr, int *str_size);
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CStatus GetBinaryVectorFromPayload(CPayloadReader payloadReader, uint8_t **values, int *dimension, int *length);
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CStatus GetFloatVectorFromPayload(CPayloadReader payloadReader, float **values, int *dimension, int *length);
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int GetPayloadLengthFromReader(CPayloadReader payloadReader);
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CStatus ReleasePayloadReader(CPayloadReader payloadReader);
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```
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