[GitHub] [ignite] SammyVimes commented on a change in pull request #9702: IGNITE-16024 B+Tree-related javadocs.

[GitBox <gi...@apache.org>]

SammyVimes commented on a change in pull request #9702:
URL: https://github.com/apache/ignite/pull/9702#discussion_r786168204



##########
File path: modules/core/src/main/java/org/apache/ignite/internal/processors/cache/persistence/tree/BPlusTree.java
##########
@@ -94,7 +94,69 @@
 import static org.apache.ignite.internal.processors.cache.persistence.tree.io.PageIoResolver.DEFAULT_PAGE_IO_RESOLVER;
 
 /**
- * Abstract B+Tree.
+ * <h3>Abstract B+Tree.</h3>
+ *
+ * B+Tree is a block-based tree structure. Each block is represented with the page ({@link PageIO}) and contains a
+ * single tree node. There are two types of pages/nodes: {@link BPlusInnerIO} and {@link BPlusLeafIO}.
+ * <p/>
+ * Every page in the tree contains a list of <i>items</i>. Item is just a fixed-size binary payload.
+ * Inner nodes and leaves may have different item sizes. There's a limit on how many items each page can hold.
+ * It is described by a {@link BPlusIO#getMaxCount(long, int)} method is the corresponding IO. There should be no empty
+ * pages in trees, so it's expected to have from {@code 1} to {@code max} items in every page.
+ * <p/>
+ * Items might have different meaning depending on the type of the page. In case of leaves, every item must describe a
+ * key and a value. In case of inner nodes, items describe only keys if {@link #canGetRowFromInner} is {@code false},
+ * or a key and a value otherwise. Items in every page are sorted according to the order dscribed by
+ * {@link #compare(BPlusIO, long, int, Object)} method. Specifics of the data stored in items are defined in the
+ * implementation and generally don't matter.
+ * <p/>
+ * All pages in the tree are devided into levels. Leaves are always at the level {@code 0}. Levels of inner pages are

Review comment:
       ```suggestion
    * All pages in the tree are divided into levels. Leaves are always at the level {@code 0}. Levels of inner pages are
   ```

##########
File path: modules/core/src/main/java/org/apache/ignite/internal/processors/cache/persistence/tree/BPlusTree.java
##########
@@ -94,7 +94,69 @@
 import static org.apache.ignite.internal.processors.cache.persistence.tree.io.PageIoResolver.DEFAULT_PAGE_IO_RESOLVER;
 
 /**
- * Abstract B+Tree.
+ * <h3>Abstract B+Tree.</h3>
+ *
+ * B+Tree is a block-based tree structure. Each block is represented with the page ({@link PageIO}) and contains a
+ * single tree node. There are two types of pages/nodes: {@link BPlusInnerIO} and {@link BPlusLeafIO}.
+ * <p/>
+ * Every page in the tree contains a list of <i>items</i>. Item is just a fixed-size binary payload.
+ * Inner nodes and leaves may have different item sizes. There's a limit on how many items each page can hold.
+ * It is described by a {@link BPlusIO#getMaxCount(long, int)} method is the corresponding IO. There should be no empty

Review comment:
       ```suggestion
    * It is defined by a {@link BPlusIO#getMaxCount(long, int)} method of the corresponding IO. There should be no empty
   ```




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