Method getRootPtrPage

src/java/simpledb/index/BTreeFile.java:1081–1097

Get a read lock on the root pointer page. Create the root pointer page and root page if necessary. @param tid - the transaction id @param dirtypages - the list of dirty pages which should be updated with all new dirty pages @return the root pointer page¶ @throws DbException @throws IOException @thr

(TransactionId tid, Map<PageId, Page> dirtypages)

	 * @throws TransactionAbortedException
	 */
	BTreeRootPtrPage getRootPtrPage(TransactionId tid, Map<PageId, Page> dirtypages) throws DbException, IOException, TransactionAbortedException {
		synchronized(this) {
			if(f.length() == 0) {
				// create the root pointer page and the root page
				BufferedOutputStream bw = new BufferedOutputStream(
						new FileOutputStream(f, true));
				byte[] emptyRootPtrData = BTreeRootPtrPage.createEmptyPageData();
				byte[] emptyLeafData = BTreeLeafPage.createEmptyPageData();
				bw.write(emptyRootPtrData);
				bw.write(emptyLeafData);
				bw.close();
			}
		}

		// get a read lock on the root pointer page
		return (BTreeRootPtrPage) getPage(tid, dirtypages, BTreeRootPtrPage.getId(tableid), Permissions.READ_ONLY);
	}

	/**
	 * Get the page number of the first empty page in this BTreeFile.