Re: Relation extension scalability

On Wed, Mar 30, 2016 at 7:19 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

Thanks for review and better comments..

> hio.c: In function ‘RelationGetBufferForTuple’:
> hio.c:231:20: error: ‘freespace’ may be used uninitialized in this
> function [-Werror=uninitialized]
> hio.c:185:7: note: ‘freespace’ was declared here
> hio.c:231:20: error: ‘blockNum’ may be used uninitialized in this
> function [-Werror=uninitialized]
> hio.c:181:14: note: ‘blockNum’ was declared here
>

I have fixed those in v20

>
> There's nothing whatsoever to prevent RelationExtensionLockWaiterCount
> from returning 0.
>
> It's also rather ugly that the call to UpdateFreeSpaceMap() assumes
> that the last value returned by PageGetHeapFreeSpace() is as good as
> any other, but maybe we can just install a comment explaining that
> point; there's not an obviously better approach that I can see.
>

Added comments..

+ if (lockWaiters)
+ /*
+ * Here we are using same freespace for all the Blocks, but that
+ * is Ok, because all are newly added blocks and have same freespace
+ * And even some block which we just added to FreespaceMap above, is
+ * used by some backend and now freespace is not same, will not harm
+ * anything, because actual freespace will be calculated by user
+ * after getting the page.
+ */
+ UpdateFreeSpaceMap(relation, firstBlock, blockNum, freespace);

Does this look good ?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com