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This commit refactors ExecScan() by moving its tuple-fetching, filtering, and projection logic into an inline-able function, ExecScanExtended(), defined in src/include/executor/execScan.h. ExecScanExtended() accepts parameters for EvalPlanQual state, qualifiers (ExprState), and projection (ProjectionInfo). Specialized variants of the execution function of a given Scan node (for example, ExecSeqScan() for SeqScan) can then pass const-NULL for unused parameters. This allows the compiler to inline the logic and eliminate unnecessary branches or checks. Each variant function thus contains only the necessary code, optimizing execution for scans where these features are not needed. The variant function to be used is determined in the ExecInit*() function of the node and assigned to the ExecProcNode function pointer in the node's PlanState, effectively turning runtime checks and conditional branches on the NULLness of epqstate, qual, and projInfo into static ones, provided the compiler successfully eliminates unnecessary checks from the inlined code of ExecScanExtended(). Currently, only ExecSeqScan() is modified to take advantage of this inline-ability. Other Scan nodes might benefit from such specialized variant functions but that is left as future work. Benchmarks performed by Junwang Zhao, David Rowley and myself show up to a 5% reduction in execution time for queries that rely heavily on Seq Scans. The most significant improvements were observed in scenarios where EvalPlanQual, qualifiers, and projection were not required, but other cases also benefit from reduced runtime overhead due to the inlining and removal of unnecessary code paths. The idea for this patch first came from Andres Freund in an off-list discussion. The refactoring approach implemented here is based on a proposal by David Rowley, significantly improving upon the patch I (amitlan) initially proposed. Suggested-by: Andres Freund <andres@anarazel.de> Co-authored-by: David Rowley <dgrowleyml@gmail.com> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Reviewed-by: Junwang Zhao <zhjwpku@gmail.com> Tested-by: Junwang Zhao <zhjwpku@gmail.com> Tested-by: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/CA+HiwqGaH-otvqW_ce-paL=96JvU4j+Xbuk+14esJNDwefdkOg@mail.gmail.com |
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PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.