Unanswered Questions
15,093 questions with no upvoted or accepted answers
18
votes
0answers
453 views
Implementation and contraindications for OPTIMIZE_FOR_SEQUENTIAL_KEY
SQL Server 2019 CTP3.1 introduced an optimization to address last-page insert contention. This takes the form of an index option called OPTIMIZE_FOR_SEQUENTIAL_KEY.
One imagines this could be an ...
13
votes
0answers
791 views
Splitting Snapshot files with MaxBCPThreads for Transactional Replication
I've just set up a publication, and I'm attempting to get the snapshot to apply faster. So far the Distribution Agent is respecting the MaxBCPThreads settings, but the Snapshot Agent is not. I'm ...
11
votes
0answers
590 views
UPDATE STATISTICS options fail in Amazon RDS SQL Server
In Amazon RDS SQL Server (any version/edition), create a temp table and update statistics on it. This works fine:
IF OBJECT_ID('tempdb..#t') IS NOT NULL
DROP TABLE #t;
GO
CREATE TABLE #t (id INT ...
9
votes
1answer
839 views
HADR high worker thread usage
Why would an availability group's number of worker threads in an HADR pool increase well beyond minimum usage of "typically, there are 3–10 shared threads" per replica?
In one case we've observed ...
8
votes
0answers
192 views
What cases benefit from the Reduce, Replicate, and Redistribute join hints?
The From Clause Documentation starting with SQL Server 2008 briefly mention 3 join hints and their basic mechanisms:
Reduce
Replicate
Redistribute
However there does not seem to be much information ...
8
votes
0answers
329 views
Cardinality estimation on tables with large cardinality variance between keys
Context
I have stumbled on an issue in SQL Azure where the Sort-operator is spilling over into TempDB due to poor row estimates.
We are querying a master table that is joined with a number of detail ...
8
votes
4answers
1k views
Foreign Key with a Constant
Let's say I have a table A, that has two columns: one is an ID for ThingA, and one is an ID for ThingB. The primary key is (ThingA, ThingB).
Next, I have a second table, but this time it's restricted ...
8
votes
0answers
625 views
Why does RDS PostgreSQL always recover on restart?
I am running an RDS instance of PostgreSQL 9.6.3: select version(); returns PostgreSQL 9.6.3 on x86_64-pc-linux-gnu [...].
I have found that after issuing a stop from the RDS console followed by a ...
8
votes
2answers
23k views
Why does CAST(1 AS SIGNED INTEGER) return a BIGINT on MySQL?
If I do CAST(1 AS SIGNED INTEGER) I always end up getting a BIGINT returned, for example:
$ mysql -u root -p --column-type-info
Enter password:
--- Copyright and help message snipped for brevity ---
...
7
votes
0answers
359 views
Database Stuck 'In Recovery' with command XTP_DB_RECOVERY
We recently converted a table to memory optimized data. Our backups have all ballooned (3x300GB files to 3x600GB files for Full, 3x50GB to 3x250GB for Diffs), and startup has been getting ...
7
votes
0answers
171 views
Constant Scan applying
This question is continuation of optimizer behavior exploration in regard to VALUES construct started here and here. I want to ask about VALUES and APPLY this time.
Using CROSS APPLY to alias an ...
7
votes
0answers
146 views
CMEMTHREAD waits during Index Optimisation in Availability Group
In a 3 node Availability group, a secondary replica will often become subject to redo lag due to the causes covered in Microsoft's documentation:
Troubleshoot: Changes on the Primary Replica are not ...
7
votes
0answers
222 views
SQL Server 2016 & 2017 Force Plan failing with reason 8695
I'm trying to force a plan using query store but it keeps failing with reason 8695 according to data in SYS.QUERY_STORE_PLAN the last_force_failure_reason_desc is 'General_Failure'.
Does anyone know ...
7
votes
1answer
667 views
Convert query in words to relational algebra
I have a follow-up question to a question I have previously asked on SO.
Instead of the query from my initial question, I want to convert the following into relational algebra:
List the names and ...
7
votes
1answer
818 views
Oracle Ref Partitioning: Deadlock due to child table row migration
My ordering application uses Oracle 11g Database. This DB has a primary table ORDERS and multiple child tables like ORDER_DETAILS, PLAN etc.
ORDERS table is LIST partitioned on STATUS column and all ...
