xtern commented on a change in pull request #7941:
URL: https://github.com/apache/ignite/pull/7941#discussion_r501722997
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File path:
modules/core/src/main/java/org/apache/ignite/internal/processors/cache/persistence/tree/io/PageIO.java
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@@ -258,6 +258,9 @@
/** */
public static final short T_MARKER_PAGE = 33;
+ /** */
+ public static final short T_INDEX_META = 34;
Review comment:
Yes, we adding two int fields into two pages.
We have 2 types of memory pages:
T_META (index partition)
T_PART_META (other partition)
We want to add 2 ints into each of them, but don't forget that IO for
T_PART_META extends IO for T_META.
In my first approach I added 2 ints into T_META, and added
PagePartitionMetaIOV3 for T_PART_META.
But since PagePartitionMetaIO "extends" PageMetaIO all offsets in
PagePartitionMetaIO was shifted and there was a problem with inheritance (for
example in PagePartitionMetaIO/V2 new methods were visible, all offsets was
redefined in PagePartitionMetaIOV3), you can imagine what it looked like in
commit with the second approach
https://github.com/apache/ignite/pull/7941/commits/036b931bd40e2ffbd519779fde86fae7343da23e
With current approach we simply create the new IO that is only used for the
"index" partition.
If you can suggest a better approach for storing 2 extra int's in the index
meta page without losing binary compatibility, please describe.
p.s. I explained this change in wiki
https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=95652384#TDE.Phase3.Cachekeyrotation.-PageMetaIOandPagePartitionMetaIO
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