d167c19295
The solution used in0ca3b1697to determine the Parallel TID Range Scan's start location was to modify the signature of table_block_parallelscan_startblock_init() to allow the startblock to be passed in as a parameter. This allows the scan limits to be adjusted before that function is called so that the limits are picked up when the parallel scan starts. The commit made it so the call to table_block_parallelscan_startblock_init uses the HeapScanDesc's rs_startblock to pass the startblock to the parallel scan. That all works ok for Parallel TID Range scans as the HeapScanDesc rs_startblock gets set by heap_setscanlimits(), but for Parallel Seq Scans, initscan() does not initialize rs_startblock, and that results in passing an uninitialized value to table_block_parallelscan_startblock_init() as noted by the buildfarm member skink, running Valgrind. To fix this issue, make it so initscan() sets the rs_startblock for parallel scans unless we're doing a rescan. This makes it so table_block_parallelscan_startblock_init() will be called with the startblock set to InvalidBlockNumber, and that'll allow the syncscan code to find the correct start location (when enabled). For Parallel TID Range Scans, this InvalidBlockNumber value will be overwritten in the call to heap_setscanlimits(). initscan() is a bit light on documentation on what's meant to get initialized where for parallel scans. From what I can tell, it looks like it just didn't matter prior to0ca3b1697that rs_startblock was left uninitialized for parallel scans. To address the light documentation, I've also added some comments to mention that the syncscan location for parallel scans is figured out in table_block_parallelscan_startblock_init. I've also taken the liberty to adjust the if/else if/else code in initscan() to make it clearer which parts apply to parallel scans and which parts are for the serial scans. Author: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/CAApHDvqALm+k7FyfdQdCw1yF_8HojvR61YRrNhwRQPE=zSmnQA@mail.gmail.com
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.
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