Examples of org.chaidb.db.index.btree.DataPage

org.chaidb.db.index.btree.DataPage
A single data page read from the database.
A page in a data file has the following layout:
```
 +--------+------------+---------------------------+ | Header | Free space |           Nodes           | +--------+------------+---------------------------+ 
```
Header: A data page has the following metadata:
```
 Size  Description 4     Number of this page 4     Page number of preceding page 4     Page number of following page 3     Doc id of this page 1     Key type of this page 4     Reserved 4 bytes 4     Flags: 0x01 - BTree internal page 0x02 - BTree leaf page 0x04 - Overflow page 0x08 - Recno internal page 0x10 - Recno leaf page 0x20 - Never delete this chain of pages 2     node number on this page 2     Upper bound of free space on page 
```
Page number of preceding page: For overflow page, it is used to store original page number. The parent page number of root page is 0.

Page number of following page: For overflow pages, it is used to store next overflow page number.

Nodes: Each node has a key and a data item. Ordinarily, the key and/or data immediately follow the flags. If the key or data is too big, it's stored on a separate 'overflow' page (or pageS, if it's really big!). In that case, the node contains a 4-byte of the first overflow page number

Overflow pages have the same header as normal pages, but simply hold raw key/data bytes. They use the 'next page' value to chain successive pages of data together.

Each node has the following format:
```
 Size  Description 4    Key Size 4    Data Size 1    Flags: 0x01 for overflow data, 0x02 for overflow key 2    size of space allocated for this node within the page n    Key/Data (4 bytes overflow page number in case key/data overflow) 
```


        final PageBufferManager buffer = btree.getBuffer();
        final BTreeSpec btreeSpec = btree.getBTreeSpec();
        PageNumber dupPageNumber = new PageNumber(nodePos.getPageNo());
        try {
            DataPage curDataPage = new DataPage(btree.getBtreeId(), dupPageNumber, btreeSpec, buffer);
            DataNode curDataNode = new DataNode(curDataPage, nodePos.getOffsetInPage());
            curDataNode.setFlags(BTreeSpec.DATA_NODE_DUP_NEXT);
            byte[] oldData = ByteTool.copyByteArray(curDataNode.getPage().getPage(), curDataNode.getNodeOffset(), (int) curDataNode.getNodeSpace());
            byte[] data = new byte[8];
            ByteTool.intToBytes(data, 0, nextNodePos.getOffsetInPage());

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        final PageBufferManager buffer = btree.getBuffer();
        final BTreeSpec btreeSpec = btree.getBTreeSpec();
        PageNumber dupPageNumber = new PageNumber(nPageNo);


        try {
            DataPage dupDataPage = new DataPage(id, dupPageNumber, btreeSpec, buffer);
            int pageCount = 0;
            while (pageCount < page && !finished) {
                NodeInfo node = new NodeInfo();
                node.nodePosition = bulkNextNodePos;
                int ret = getNode(dupDataPage, node);
                bulkNextNodePos = node.nodeNextPosition;
                if ((ret & DUP_FINISHED) == DUP_FINISHED) {
                    finished = true;
                    if ((ret & DUP_NEXT) == DUP_NEXT) {
                        break;
                    }
                }
                if ((ret & DUP_DATA) == DUP_DATA) {
                    cache.add(node);
                } else if ((ret & DUP_NEXT) == DUP_NEXT) {
                    if (bulkNextNodePos.getPageNo() == nPageNo) {
                        continue;
                    } else {
                        if (cache.size() > 0) {
                            pageCount++;
                        }
                        if (pageCount < page) {
                            nPageNo = bulkNextNodePos.getPageNo();
                            buffer.releasePage(id, dupPageNumber, false);
                            dupPageNumber = new PageNumber(nPageNo);
                            dupDataPage = new DataPage(id, dupPageNumber, btreeSpec, buffer);
                        }
                    }
                } else {
                    logger.error("Failed to get next dup node.");
                }

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        dupNextCountForNextNode = 0;


        int curPageNo = nodePos.getPageNo();
        PageNumber dupPageNumber = new PageNumber(curPageNo);
        try {
            DataPage dupDataPage = new DataPage(id, dupPageNumber, btreeSpec, buffer);
            NodeInfo node = new NodeInfo();
            node.nodePosition = nodePos;
            while (true) {
                int ret = getNode(dupDataPage, node);
                if ((ret & DUP_FINISHED) == DUP_FINISHED) {
                    finished = true;
                    if ((ret & DUP_NEXT) == DUP_NEXT) {
                        break;
                    }
                }
                if ((ret & DUP_DATA) == DUP_DATA) {
                    return node;
                } else if ((ret & DUP_NEXT) == DUP_NEXT) {
                    node.nodePosition = node.nodeNextPosition;
                    if (node.nodeNextPosition.getPageNo() != curPageNo) {
                        curPageNo = node.nodeNextPosition.getPageNo();
                        buffer.releasePage(id, dupPageNumber, false);
                        dupPageNumber = new PageNumber(curPageNo);
                        dupDataPage = new DataPage(id, dupPageNumber, btreeSpec, buffer);
                    }
                } else {
                    logger.error("Failed to get next dup node.");
                    break;
                }

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Related Classes of org.chaidb.db.index.btree.DataPage

org.chaidb.db.index.btree.bufmgr.Page

org.chaidb.db.index.btree.bufmgr.PageNumber

org.chaidb.db.index.btree.hbt.HyperBTreeBasicIterator

org.chaidb.db.index.btree.hbt.HyperBTreeCachedIterator

org.chaidb.db.index.btree.hbt.HyperBTreeIterator

org.chaidb.db.log.logrecord.BTreeAddRemoveLogRecord

org.chaidb.db.log.logrecord.BTreeFreeOverflowPageLogRecord

org.chaidb.db.log.logrecord.BTreeNewPageLogRecord

org.chaidb.db.log.logrecord.BTreeReplLogRecord

org.chaidb.db.exception.ChaiDBException

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