The Halloween Problem—Part 4
SQL Server Halloween Protection and the query optimizer. Redundant sorts and other non-eager table spool options.
Articles
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The Halloween Problem—Part 3
SQL Server Halloween Protection special optimizations for the MERGE statement. Hole-filling and rowset sharing.
The Halloween Problem—Part 2
When SQL Server Halloween Protection is needed for INSERT and DELETE statements. Constraint checking and phase separation.
The Halloween Problem—Part 1
Halloween Protection for SQL Server UPDATE queries. Why protection is needed and how it is implemented.
Incorrect Results with Merge and Indexed Views
Incorrect results from a SQL Server query using MERGE, indexed views and foreign keys.
A creative use of IGNORE_DUP_KEY
Adding the IGNORE_DUP_KEY option to an existing primary key without downtime. How the execution plans generated for IGNORE_DUP_KEY work.
Optimizing T-SQL queries that change data
Optimizing the performance of SQL Server INSERT, UPDATE, DELETE, and MERGE statements. Execution plan analysis and undocumented trace flags. Narrow (per-row) and wide (per-index) plans.
MERGE Bug with Filtered Indexes
A SQL Server bug with unique filtered indexes. Covers narrow update plans and the Split, Sort, Collapse operator combination.
Cardinality Estimation Bug with Lookups
Incorrect SQL Server estimated row counts on Key and RID Lookup operators where a Filter is applied.
Why Doesn’t Partition Elimination Work?
SQL Server can fail to eliminate partitions from a query due to implicit type conversion.
Compute Scalars, Expressions and Execution Plan Performance
How the SQL Server Compute Scalar operator works internally.
Deletes that Split Pages and Forwarded Ghosts
Slow SQL Server DELETE peformance caused by unexpected page splitting or forwarded ghost records.
Temporary Table Caching Explained
Internal details of SQL Server temporary table and table variable caching.
Temporary Table Caching in Stored Procedures
How SQL Server temporary table caching can affect statistics, execution plans, and recompilations in unexpected ways.
Parallel Execution Plans Suck
Why TOP may not work well with SQL Server parallel queries.
Query Optimizer Deep Dive—Part 4
Internal operation of the SQL Server query optimizer. Writing queries that will take advantage of the optimizer's relational reasoning.
Query Optimizer Deep Dive—Part 3
SQL Server query optimizer memo structure, search stages, and final plan selection.
Query Optimizer Deep Dive—Part 2
Cost-based optimization in the SQL Server query optimizer, the input tree, properties, and rules.