Query optimizations

src/main/java/it/cavallium/strangedb/database/blocks/DatabaseBlocksIO.java

@@ -55,6 +55,24 @@ public class DatabaseBlocksIO implements IBlocksIO {
 		return fileIO.readAt(blockInfo.getIndex(), blockInfo.getSize());
 	}
 
+	public ByteBuffer readBlockSizeAndLastElementOfReferencesList(long blockId) throws IOException {
+		if (blockId == EMPTY_BLOCK_ID) {
+			return ByteBuffer.wrap(new byte[0]);
+		}
+		if (blockId == ERROR_BLOCK_ID) {
+			throw new IOException("Errored block id");
+		}
+		if (blockId < 0) {
+			throw new IOException("Block id " + blockId + " is not valid");
+		}
+		BlockInfo blockInfo = blocksMetadata.getBlockInfo(blockId);
+		if (blockInfo.getSize() >= Integer.BYTES * 2 + Long.BYTES) {
+			return fileIO.readAt(blockInfo.getIndex() + blockInfo.getSize() - (Integer.BYTES + Long.BYTES), Integer.BYTES + Long.BYTES);
+		} else {
+			return fileIO.readAt(blockInfo.getIndex(), blockInfo.getSize());
+		}
+	}
+
 	@Override
 	public void close() {
 

src/main/java/it/cavallium/strangedb/database/references/DatabaseReferencesIO.java

@@ -53,4 +53,15 @@ public class DatabaseReferencesIO implements IReferencesIO {
 		}
 		return blocksIO.readBlock(blockId);
 	}
+
+	public ByteBuffer readFromReferenceSizeAndLastElementOfReferencesList(long reference) throws IOException {
+		long blockId;
+		lock.readLock().lock();
+		try {
+			blockId = referencesMetadata.getReferenceBlockId(reference);
+		} finally {
+			lock.readLock().unlock();
+		}
+		return blocksIO.readBlockSizeAndLastElementOfReferencesList(blockId);
+	}
 }