Add some documentation for supported MySQL replication modes #1906
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Signed-off-by: Matt Lord <[email protected]>
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deepthi
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| Vitess requires the use of [Row-Based Replication (RBR)](https://dev.mysql.com/doc/refman/en/replication-formats.html) with [GTIDs](https://dev.mysql.com/doc/refman/en/replication-gtids.html) enabled: [`--binlog-row-format=ROW`](https://dev.mysql.com/doc/refman/en/replication-options-binary-log.html#sysvar_binlog_format) and [`--gtid-mode=ON`](https://dev.mysql.com/doc/refman/en/replication-options-gtids.html#sysvar_gtid_mode). | ||
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| Vitess also recommends [`FULL`](https://dev.mysql.com/doc/refman/en/replication-options-binary-log.html#sysvar_binlog_row_image) binary log images in order to support all manner of transformations in [VReplication workflows](../../vreplication/vreplication/), but in v17 we added *experimental* support for [`--binlog-row-image=NOBLOB`](https://dev.mysql.com/doc/refman/en/replication-options-binary-log.html#sysvar_binlog_row_image) (see [#1290](https://github.com/vitessio/vitess/pull/12905) for more details). |
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What would it take to move NOBLOB out of "experimental"? I'm curious why this was done as experimental whereas we seem to be more confident about our ability to support PARTIAL_JSON.
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We expect and know that some things will fail with NOBLOB, because we lose information in the binary log events. There's no before OR after image value for the BLOB/TEXT columns when not updated in the row, which means we lose information and we know that some OnlineDDL and Materialize workflows will fail because we lack information to perform accurate transformations. We also know e.g. that changing the PK definitions on a table on the target will cause MoveTables workflows to fail if you update the PK column values in the table. That's what this is about: https://github.com/vitessio/vitess/pull/17345/files#r1892674955
With PARTIAL_JSON nothing should fail. That's because we don't lose information: there's always the BEFORE image value along with a diff in the AFTER image that can be applied to that before value in order to get the full after value.
Docs for vitessio/vitess#17345
Preview: https://deploy-preview-1906--vitess.netlify.app/docs/22.0/reference/features/mysql-replication/#mysql-replication-modes