Revert "Merge pull request #1 from sdudoladov/v5-idle-in-transaction-…#3
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sdudoladov merged 1 commit intomasterfrom Jan 19, 2022
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Revert "Merge pull request #1 from sdudoladov/v5-idle-in-transaction-…#3sdudoladov merged 1 commit intomasterfrom
sdudoladov merged 1 commit intomasterfrom
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sdudoladov
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Aug 22, 2022
We've heard a couple of reports of people having trouble with multi-gigabyte-sized query-texts files. It occurred to me that on 32-bit platforms, there could be an issue with integer overflow of calculations associated with the total query text size. Address that with several changes: 1. Limit pg_stat_statements.max to INT_MAX / 2 not INT_MAX. The hashtable code will bound it to that anyway unless "long" is 64 bits. We still need overflow guards on its use, but this helps. 2. Add a check to prevent extending the query-texts file to more than MaxAllocHugeSize. If it got that big, qtext_load_file would certainly fail, so there's not much point in allowing it. Without this, we'd need to consider whether extent, query_offset, and related variables shouldn't be off_t not size_t. 3. Adjust the comparisons in need_gc_qtexts() to be done in 64-bit arithmetic on all platforms. It appears possible that under duress those multiplications could overflow 32 bits, yielding a false conclusion that we need to garbage-collect the texts file, which could lead to repeatedly garbage-collecting after every hash table insertion. Per report from Bruno da Silva. I'm not convinced that these issues fully explain his problem; there may be some other bug that's contributing to the query-texts file becoming so large in the first place. But it did get that big, so #2 is a reasonable defense, and #3 could explain the reported performance difficulties. (See also commit 8bbe4cb, which addressed some related bugs. The second Discussion: link is the thread that led up to that.) This issue is old, and is primarily a problem for old platforms, so back-patch. Discussion: https://postgr.es/m/CAB+Nuk93fL1Q9eLOCotvLP07g7RAv4vbdrkm0cVQohDVMpAb9A@mail.gmail.com Discussion: https://postgr.es/m/5601D354.5000703@BlueTreble.com
sdudoladov
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Jan 11, 2024
checkExtensionMembership() set the DUMP_COMPONENT_SECLABEL and DUMP_COMPONENT_POLICY flags for extension member objects, even though we lack any infrastructure for tracking extensions' initial settings of these properties. This is not OK. The result was that a dump would always include commands to set these properties for extension objects that have them, with at least three negative consequences: 1. The restoring user might not have privilege to set these properties on these objects. 2. The properties might be incorrect/irrelevant for the version of the extension that's installed in the destination database. 3. The dump itself might fail, in the case of RLS properties attached to extension tables that the dumping user lacks privilege to LOCK. (That's because we must get at least AccessShareLock to ensure that we don't fail while trying to decompile the RLS expressions.) When and if somebody cares to invent initial-state infrastructure for extensions' RLS policies and security labels, we could think about finding another way around problem #3. But in the absence of such infrastructure, this whole thing is just wrong and we shouldn't do it. (Note: this applies only to ordinary dumps; binary-upgrade dumps still dump and restore extension member objects separately, with all properties.) Tom Lane and Jacob Champion. Back-patch to all supported branches. Discussion: https://postgr.es/m/00d46a48-3324-d9a0-49bf-e7f0f11d1038@timescale.com
sdudoladov
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Aug 11, 2025
There've been a few complaints that it can be overly difficult to figure out why the planner picked a Memoize plan. To help address that, here we adjust the EXPLAIN output to display the following additional details: 1) The estimated number of cache entries that can be stored at once 2) The estimated number of unique lookup keys that we expect to see 3) The number of lookups we expect 4) The estimated hit ratio Technically #4 can be calculated using #1, #2 and #3, but it's not a particularly obvious calculation, so we opt to display it explicitly. The original patch by Lukas Fittl only displayed the hit ratio, but there was a fear that might lead to more questions about how that was calculated. The idea with displaying all 4 is to be transparent which may allow queries to be tuned more easily. For example, if #2 isn't correct then maybe extended statistics or a manual n_distinct estimate can be used to help fix poor plan choices. Author: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com> Author: Lukas Fittl <lukas@fittl.com> Reviewed-by: David Rowley <dgrowleyml@gmail.com> Reviewed-by: Andrei Lepikhov <lepihov@gmail.com> Reviewed-by: Robert Haas <robertmhaas@gmail.com> Discussion: https://postgr.es/m/CAP53Pky29GWAVVk3oBgKBDqhND0BRBN6yTPeguV_qSivFL5N_g%40mail.gmail.com
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…patch"
This reverts commit 73dc9f8, reversing
changes made to e0e567a.