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  • SQL Server 2019 Aggregate Splitting

    The SQL Server 2019 query optimizer has a new trick available to improve the performance of large aggregations. The new exploration abilities are encoded in two new closely-related optimizer rules: GbAggSplitToRanges SelOnGbAggSplitToRanges The extended event query_optimizer_batch_mode_agg_split is provided to track when this new ...
    Posted to Page Free Space (Weblog) by Paul White on August 3, 2020
  • A bug with Halloween Protection and the OUTPUT Clause

    Background The OUTPUT clause can be used to return results from an INSERT, UPDATE, DELETE, or MERGE statement. The data can be returned to the client, inserted to a table, or both. There are two ways to add OUTPUT data to a table: Using OUTPUT INTO With an outer INSERT statement. For example: -- Test table DECLARE @Target ...
    Posted to Page Free Space (Weblog) by Paul White on August 3, 2020
  • Pulling Group By Above a Join

    One of the transformations available to the SQL Server query optimizer is pulling a logical Group By (and any associated aggregates) above a Join. Visually, this means transforming a tree of logical operations from: …to this: The above diagrams are logical representations. They need to be implemented as physical operators to appear in an ...
    Posted to Page Free Space (Weblog) by Paul White on August 3, 2020
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