Different object types within the two systems are mapped as follows:
The full replication of information operates as follows:
Data is extracted from the source database using the standard extractor, for example by reading the row change data from the binlog in MySQL.
The Section 9.4.5, “ColumnName Filter” filter is used to extract column name information from the database. This enables the row-change information to be tagged with the corresponding column information. The data changes, and corresponding row names, are stored in the THL.
The Section 9.4.26, “PrimaryKey Filter” filter is used to extract primary key data from the source tables.
On the Applier replicator, the THL data is read and written into batch-files in the character-separated value format.
The information in these files is change data, and contains not only
the original row values from the source tables, but also metadata
about the operation performed (i.e.
UPDATE, and the primary key of
for each table. All
statements are recorded as a
DELETE of the existing data,
INSERT of the new data.
In addition to these core operation types, the batch applier can also
be configured to record
operations that result in
DELETE rows. This enables
Redshift to process the update information more simply than performing
A second process uses the CSV stage data and any existing data, to build a materialized view that mirrors the source table data structure.
The staging files created by the replicator are in a specific format that incorporates change and operation information in addition to the original row data.
The format of the files is a character separated values file, with
each row separated by a newline, and individual fields separated by
0x01. This is
supported by Hive as a native value separator.
The content of the file consists of the full row data extracted from the Source, plus metadata describing the operation for each row, the sequence number, and then the full row information.
|Operation||Sequence No||Table-specific primary key||DateTime||Table-columns...|
||PRIMARYKEY||DATATIME of source table commit|
The operation field will match one of the following values
Row is an |
Row is |
Row is an |
Row is an |
For example, the MySQL row from an
| 3 | #1 Single | 2006 | Cats and Dogs (#1.4) |
Is represented within the CSV staging files generated as:
"I","5","3","2014-07-31 14:29:17.000","3","#1 Single","2006","Cats and Dogs (#1.4)"
The character separator, and whether to use quoting, are configurable within the replicator when it is deployed. For Redshift, the default behavior is to generate quoted and comma separated fields.