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  • Memory Allocated To Plan Caching

    I could complain about Entity Framework, but there is probably nothing that has not already been aired. So instead, I will complain about the lack of tuning options in SQL Server's Memory Allocated To Plan Caching. As of SQL Server versions 2005 SP2 and 2008, the formula is 75% from the first 0-4GB, 10% from 4-64GB and 5% of the remaining ...
    Posted to Joe Chang (Weblog) by jchang on August 12, 2017
  • Azure database_id inconsistencies

    I am working on improvements to my SQL ExecStats tool, including Azure support. Previously, I had put try catch blocks around everything that bombs in Azure. Now I am putting IF EXISTS tests around SQL referencing system views and procedures not in Azure an other. One of issues I encountered is that there is an inconsistency between DB_ID() and ...
    Posted to Joe Chang (Weblog) by jchang on May 23, 2017
  • re: Fixing the Query Optimizer Cost Model

    changing the default CTOP is nice, but the most important matter is for the cost model to correctly model IO cost in parallel execution, i.e., scale IO cost with parallelism. Second most important is probably parallelism and NUMA, scaling is great with all threads on single socket, questionable over multiple sockets - redistribute streams having ...
    Posted to Joe Chang (Weblog) by jchang on March 16, 2017
  • re: Fixing the Query Optimizer Cost Model

    It would be a cold day in hell before MS allows the cost model to be tunable, but MS said the same thing about PAE (used by AWE) back in 1997/8. There is a trace flag for the CPU/IO ratio, see Paul White's posts? But I do not think this is helpful because neither the current cost model CPU or IO components constitute a reasonable representation of ...
    Posted to Joe Chang (Weblog) by jchang on February 26, 2017
  • re: Fixing the Query Optimizer Cost Model

    hello Glenn, that is correct, I endorse single socket with the Xeon E5 v4 processor that is capable of 2-way. You could buy either a UP or DP motherboard from Supermicro with 1-socket populated. Or you could buy a Dell or HP server with 1 E5v4. Of course the E3 is not chump change, 16 PCI-E lanes is workable if I could get 4 x4 + the DMI equiv ...
    Posted to Joe Chang (Weblog) by jchang on February 21, 2017
  • Fixing the Query Optimizer Cost Model

    The model for the cost of operations used by the SQL Server query optimizer to produce an execution plan is rather simple. It has been largely unchanged since SQL Server version 7, RTM in 1998. Back then, SQL Server had not yet achieved tier 1 status with commensurate development resources. Some adjustments were made in version ...
    Posted to Joe Chang (Weblog) by jchang on February 20, 2017
  • re: Parallel Execution on SQL Server 2016

    The key to Hyper-Threading is in there being significant round-trip memory access no-op cycles. For transactions, this is very true. In other posts, I have suggested that this might be around 5% of instructions, meaning that perhaps only 12% of cycles are actually used by a thread. Hence scaling with HT is almost linear in the absence of ...
    Posted to Joe Chang (Weblog) by jchang on February 5, 2017
  • re: Parallel Execution on SQL Server 2016

    In principle, Azure, AWS etc. are good options to have. Very few companies have the resources to hyper-optimize IT infrastructure administration. Some &nbsp;have fallen into the trap of gold-bricking, using &quot;enterprise&quot; SANs, i.e. about $6K per HDD. Other have become obstructors of IT. The problem is that every time something good comes ...
    Posted to Joe Chang (Weblog) by jchang on February 5, 2017
  • Parallel Execution on SQL Server 2016

    There are a number of interesting questions in parallel execution performance that can be investigated using the TPC-H kit, which has a data generator. There are also supplemental files that accompany published results. Important questions in parallel execution are: scaling versus degree of parallelism (DOP) on physical cores, ...
    Posted to Joe Chang (Weblog) by jchang on February 1, 2017
  • re: Saving a Few Lines of Code by Performing Multiple Operations in a Single Command

    change the order to DROP TABLE dbo.Table2, dbo.Table1 to avoid the foreign key constraint
    Posted to Louis Davidson (Weblog) by jchang on January 23, 2017
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