Re: Hash Indexes

On Thu, Jun 16, 2016 at 12:58 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:

I have a question regarding code changes in *_hash_first*.

+ /*
+ * Conditionally get the lock on primary bucket page for search
while
+ * holding lock on meta page. If we have to wait, then release the
meta
+ * page lock and retry it in a hard way.
+ */
+ bucket = _hash_hashkey2bucket(hashkey,
+
metap->hashm_maxbucket,
+
metap->hashm_highmask,
+
metap->hashm_lowmask);
+
+ blkno = BUCKET_TO_BLKNO(metap, bucket);
+
+ /* Fetch the primary bucket page for the bucket */
+ buf = ReadBuffer(rel, blkno);
+ if (!ConditionalLockBufferShared(buf))

Here we try to take lock on bucket page but I think if successful we do not
recheck whether any split happened before taking lock. Is this not
necessary now?

Also below "if" is always true as we enter here only when outer "if
(retry)" is true.
+ if (retry)
+ {
+ if (oldblkno == blkno)
+ break;
+ _hash_relbuf(rel, buf);
+ }

--
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com