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    Avro Demo Description

    Last updated: 2023-08-25 15:33:47

      Key Logic Description

      Files in the demo are as described below, with the Java demo as an example.
      consumerDemo-avro-java\\src\\main\\resources\\avro-tools-1.8.2.jar: The tool used to generate Avro protocol code.
      consumerDemo-avro-java\\src\\main\\java\\com\\tencent\\subscribe\\avro: The directory of the Avro tool-generated code.
      consumerDemo-avro-java\\src\\main\\resources\\Record.avsc: The protocol definition file.
      14 structures (also known as schemas in Avro) are defined in Record.avsc. The main data structure is record, which is used to represent a data record in binlog. The record structure is as follows. Other data structures can be viewed in Record.avsc.
       {
          "namespace": "com.tencent.subscribe.avro",    // The last schema in `Record.avsc`, with `name` displayed as `Record`.
          "type": "record",    
          "name": "Record",     // `name` is displayed as `Record`, indicating the format of the data consumed from Kafka.
          "fields": [
            {
              "name": "id",     // `id` indicates a globally incremental ID. More record values are explained as follows:
              "type": "long",
              "doc": "unique id of this record in the whole stream"
            },
            {
              "name": "version",  // `version` indicates the protocol version.
              "type": "int",
              "doc": "protocol version"  
            },
            {
              "name": "messageType",   // Message type
              "aliases": [
                "operation"
              ],
              "type": {
                "namespace": "com.tencent.subscribe.avro",
                "name": "MessageType",
                "type": "enum",
                "symbols": [
                  "INSERT",
                  "UPDATE",
                  "DELETE",
                  "DDL",
                  "BEGIN",
                  "COMMIT",
                  "HEARTBEAT",
                  "CHECKPOINT",
                  "ROLLBACK"          
                  "STATEMENT",         
                  "INIT_DDL",          
                  "INIT_INSERT"
                ]
              }
            },  
            {
             ......
            },     
       }
      Fields in a record are as explained below:
      Field Name in Record
      Description
      id
      The globally incremental ID
      version
      The protocol version, which is v1 currently.
      messageType
      The message type. Enumerated values: INSERT, UPDATE, DELETE, DDL, BEGIN, COMMIT, HEARTBEAT, CHECKPOINT, STATEMENT，INIT_DDL，INIT_INSERT.
      INIT_DDL: DDL operation on full data; DDL: DDL operation on incremental data; INIT_INSERT: INSERT operation on full data; INSERT: INSERT operation on incremental data.
      fileName
      The name of the binlog file where the current record is located.
      position
      The end offset of the current record in the binlog in the format of End_log_pos@binlog file number. For example, if the current record is in file mysql-bin.000004 and the end offset is 2196, then the value of this parameter will be 2196@4.
      safePosition
      The start offset of the current transaction in the binlog, which is in the same format as described above.
      timestamp
      The time when the data was written to the binlog, which is a UNIX timestamp in seconds.
      gtid
      The current GTID, such as c7c98333-6006-11ed-bfc9-b8cef6e1a231:9.
      transactionId
      The transaction ID, which is generated only for COMMIT events.
      serverId
      The server ID of the source database, which can be viewed by running SHOW VARIABLES LIKE 'server_id'.
      threadId
      The ID of the session that committed the current transaction, which can be viewed by running SHOW processlist;.
      sourceType
      The source database type, which currently can only be MySQL.
      sourceVersion
      The source database version, the value of which is the same as that of select version();
      schemaName
      Database name
      tableName
      Table name
      objectName
      Format: Database name.table name
      columns
      The definitions of columns in the table
      oldColumns
      The data of the row before DML execution. If the message is an INSERT message, the array will be null. There are 12 element types in the array: Integer, Character, Decimal, Float, Timestamp, DateTime, TimestampWithTimeZone, ‍inaryGeometry, TextGeometry, BinaryObject, TextObject, and EmptyObject. For more information, see the demo.
      newColumns
      The data of the row after DML execution. If the message is a DELETE message, the array will be null. There are 12 element types in the array: Integer, Character, Decimal, Float, Timestamp, DateTime, TimestampWithTimeZone, ‍inaryGeometry, TextGeometry, BinaryObject, TextObject, and EmptyObject. For more information, see the demo.
      sql
      The DDL SQL statement.
      executionTime
      The DDL execution duration in seconds.
      heartbeatTimestamp
      The timestamp of the heartbeat message in seconds. This field is present only for heartbeat messages.
      syncedGtid
      The collection of GTIDs parsed by DTS in the format of c7c98333-6006-11ed-bfc9-b8cef6e1a231:1-13.
      fakeGtid
      Whether the current GTID is forged. If gtid_mode is not enabled, DTS will forge a GTID.
      pkNames
      If the table in the source database has a primary key, this parameter will be carried in the DML message; otherwise, it will not be carried.
      readerTimestamp
      The time when DTS processed the current data record, which is a UNIX timestamp in milliseconds.
      tags
      The status_vars in QueryEvent. For more information, see QueryEvent.
      total
      The total number of message segments if the message is segmented. This field is invalid on the current version (version=1) and is reserved for extension.
      index
      The index of message segments if the message is segmented. This field is invalid on the current version (version=1) and is reserved for extension.
      The field describing column attributes in a record is Field, including the following four attributes:
      name: The column name.
      dataTypeNumber: The type of the data recorded in the binlog. For values, see MySQL source code documentation.
      isKey: Whether the current key is the primary key.
      originalType: The type defined in DDL.

      Database field mappings

      The following lists the mappings between database (such as MySQL) field types and data types defined in the Avro protocol.
      Type in MySQL
      Corresponding Type in Avro
      MYSQL_TYPE_NULL
      EmptyObject
      MYSQL_TYPE_INT8
      Integer
      MYSQL_TYPE_INT16
      Integer
      MYSQL_TYPE_INT24
      Integer
      MYSQL_TYPE_INT32
      Integer
      MYSQL_TYPE_INT64
      Integer
      MYSQL_TYPE_BIT
      Integer
      MYSQL_TYPE_YEAR
      DateTime
      MYSQL_TYPE_FLOAT
      Float
      MYSQL_TYPE_DOUBLE
      Float
      MYSQL_TYPE_VARCHAR
      Character
      MYSQL_TYPE_STRING
      Character. If the original type is binary, this type will correspond to BinaryObject.
      MYSQL_TYPE_VAR_STRING
      Character. If the original type is varbinary, this type will correspond to BinaryObject.
      MYSQL_TYPE_TIMESTAMP
      Timestamp
      MYSQL_TYPE_DATE
      DateTime
      MYSQL_TYPE_TIME
      DateTime
      MYSQL_TYPE_DATETIME
      DateTime
      MYSQL_TYPE_TIMESTAMP_NEW
      Timestamp
      MYSQL_TYPE_DATE_NEW
      DateTime
      MYSQL_TYPE_TIME_NEW
      DateTime
      MYSQL_TYPE_DATETIME_NEW
      DateTime
      MYSQL_TYPE_ENUM
      TextObject
      MYSQL_TYPE_SET
      TextObject
      MYSQL_TYPE_DECIMAL
      Decimal
      MYSQL_TYPE_DECIMAL_NEW
      Decimal
      MYSQL_TYPE_JSON
      TextObject
      MYSQL_TYPE_BLOB
      BinaryObject
      MYSQL_TYPE_TINY_BLOB
      BinaryObject
      MYSQL_TYPE_MEDIUM_BLOB
      BinaryObject
      MYSQL_TYPE_LONG_BLOB
      BinaryObject
      MYSQL_TYPE_GEOMETRY
      BinaryObject
      
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