jt2594838 commented on a change in pull request #1169:
URL: https://github.com/apache/incubator-iotdb/pull/1169#discussion_r428411974
##########
File path:
server/src/main/java/org/apache/iotdb/db/engine/storagegroup/TsFileResource.java
##########
@@ -571,4 +603,56 @@ public long getTimePartitionWithCheck() throws
PartitionViolationException {
}
return partitionId;
}
+
+ /**
+ * Create a hardlink for the TsFile and modification file (if exists)
+ * The hardlink with have a suffix like ".{sysTime}_{randomLong}"
+ * @return a new TsFileResource with its file changed to the hardlink or
null the hardlink
+ * cannot be created.
+ */
+ public TsFileResource createHardlink() {
+ if (!file.exists()) {
+ return null;
+ }
+
+ TsFileResource newResource;
+ try {
+ newResource = new TsFileResource(this);
+ } catch (IOException e) {
+ logger.error("Cannot create hardlink for {}", file, e);
+ return null;
+ }
+
+ while (true) {
+ String hardlinkSuffix = "." + System.currentTimeMillis() + "_" +
random.nextLong();
+ File hardlink = new File(file.getAbsolutePath() + hardlinkSuffix);
+
+ try {
+ Files.createLink(Paths.get(hardlink.getAbsolutePath()),
Paths.get(file.getAbsolutePath()));
+ newResource.setFile(hardlink);
+ if (modFile != null && modFile.exists()) {
+ newResource.setModFile(modFile.createHardlink());
+ }
+ break;
+ } catch (FileAlreadyExistsException e) {
+ // retry a different name if the file is already created
+ } catch (IOException e) {
+ logger.error("Cannot create hardlink for {}", file, e);
+ return null;
+ }
+ }
+ return newResource;
+ }
+
+ public synchronized void setModFile(ModificationFile modFile) {
+ this.modFile = modFile;
+ }
+
+ public long getMaxVersion() {
+ long maxVersion = 0;
+ if (historicalVersions != null) {
+ maxVersion = Collections.max(historicalVersions);
Review comment:
How large could it be? A file of several hundred MBs will only have one
version, which only takes 8 bytes. Even if several such files are merged into
one file of several GBs, the version will not take more than 1 KB.
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