Remove dependent realisations by Ericson2314 · Pull Request #14247 · NixOS/nix

Ericson2314 · 2025-10-14T18:19:42Z

Motivation

This progress on #11896. It introduces some issues temporarily which will be fixed when #11928 is fixed.

Context

The SQL tables are left in place because there is no point inducing a migration now, when we will be immediately landing more changes after this that also require schema changes. They will simply be ignored by in this commit, and so all data will be preserved.

Depends on #14465
Depends on #14425
Depends on #13942
Depends on #14793

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This will allow us to more accurately test dropping support for dependent realisations, by separating the tests that should not change from the tests that should. I do that change in PR NixOS#14247, but even if for some reasons we don't end up doing this soon, I think it is still good to separate the test data this way so we have the option of doing that at some point.

dpulls · 2025-11-06T18:56:26Z

🎉 All dependencies have been resolved !

dpulls · 2025-11-24T23:50:59Z

🎉 All dependencies have been resolved !

Ericson2314 · 2025-11-26T23:30:57Z

src/libstore/ca-specific-schema.sql

I need to figure out how the migration for this works. CC @edolstra, do you know?

Ericson2314 · 2025-12-15T21:04:33Z

src/libstore/local-store.cc

+            throw Error(
+                "Migrating the database schema for the '%s' experimental feature is not yet supported.\n\n"
+                "Either downgrade Nix to a version that supports the old schema, "
+                "or disable the '%s' experimental feature.\n\n"
+                "Note: Disabling the experimental feature will safely leave all existing data intact.",
+                showExperimentalFeature(Xp::CaDerivations),
+                showExperimentalFeature(Xp::CaDerivations));


This is the temporary so I can make progress on this stuff. When I am done and we have something that looks stable, we can then think about how to write this migration.

That's not a great migration. I changed it to this instead:

From 9366ff4c02275d2d1bf35cd27d94ba5952071485 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io> Date: Tue, 16 Dec 2025 19:53:12 +0100 Subject: [PATCH] local-store: better migration for RealisationsRefs removal MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The previous commit removed usage of the RealisationsRefs table but threw an error for existing databases with CA derivations enabled, blocking deployment entirely. Instead of erroring, keep the old table around for backwards compatibility with older Nix versions that may still share the database. They will continue to populate it while new Nix simply ignores it. This allows mixed-version deployments during upgrades. Signed-off-by: Jörg Thalheim <joerg@thalheim.io> --- src/libstore/local-store.cc | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc index 080b454b6..df6d5cc7d 100644 --- a/src/libstore/local-store.cc +++ b/src/libstore/local-store.cc @@ -598,14 +598,15 @@ void LocalStore::upgradeDBSchema(State & state) "20251013-remove-realisations-refs", }); } else if (!schemaMigrations.contains("20251013-remove-realisations-refs")) { - /* CA drvs previously enabled with old schema. */ - throw Error( - "Migrating the database schema for the '%s' experimental feature is not yet supported.\n\n" - "Either downgrade Nix to a version that supports the old schema, " - "or disable the '%s' experimental feature.\n\n" - "Note: Disabling the experimental feature will safely leave all existing data intact.", - showExperimentalFeature(Xp::CaDerivations), - showExperimentalFeature(Xp::CaDerivations)); + /* CA drvs previously enabled with old schema. The new code no + longer uses the RealisationsRefs table, but we keep it around + for backwards compatibility with older Nix versions that may + still share this database. They will continue to populate it, + but we simply ignore it. */ + debug("executing Nix database schema migration '%s'...", "20251013-remove-realisations-refs"); + + SQLiteTxn txn(state.db); + commitAndMarkMigrations(txn, {"20251013-remove-realisations-refs"}); } } } -- 2.50.1

Otherwise I wouldn't be able to upgrade at all. But I am wondering, why can we not keep the migration linear and just ignore the fact that we have a few empty tables in the schema? It would help when people upgrade/downgrade Nix versions.

I was worried about the foreign keys, but I guess the on-delete cascade will help with that?

As @Mic92 and I discussed, there is no more schema change at all.

dpulls · 2025-12-16T04:14:32Z

🎉 All dependencies have been resolved !

xokdvium · 2025-12-17T00:50:32Z

src/libstore/include/nix/store/sqlite.hh

+    /**
+     * Execute a SQL statement. The string must be null-terminated.
+     */
+    void exec(const char * stmt);
+
+    void exec(const std::string & stmt)
+    {
+        exec(stmt.c_str());
+    }


Seems like some leftover thing?

This progress on NixOS#11896. It introduces some issues temporarily which will be fixed when NixOS#11928 is fixed. The SQL tables are left in place because there is no point inducing a migration now, when we will be immediately landing more changes after this that also require schema changes. They will simply be ignored by in this commit, and so all data will be preserved.

xokdvium · 2025-12-17T00:58:04Z

src/libstore/store-api.cc

+    std::vector<const Realisation *> realisations;
    for (auto & path : paths) {
        storePaths.insert(path.path());
        if (auto * realisation = std::get_if<Realisation>(&path.raw)) {
            experimentalFeatureSettings.require(Xp::CaDerivations);
-            toplevelRealisations.insert(*realisation);
+            realisations.push_back(realisation);


Is this some kind of optimisation? We can split this out right?

Discussed 1-1, is because I get rid of the closure method because we didn't really need it any more. This is just some inlined remnants of it.

…isations Remove dependent realisations

Ericson2314 requested a review from edolstra as a code owner October 14, 2025 18:19

github-actions bot added documentation new-cli Relating to the "nix" command with-tests Issues related to testing. PRs with tests have some priority store Issues and pull requests concerning the Nix store labels Oct 14, 2025

Ericson2314 mentioned this pull request Oct 15, 2025

Realisations use regular drv paths again #12464

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Ericson2314 force-pushed the no-dependent-realisations branch 4 times, most recently from c03e01e to d795f87 Compare October 20, 2025 20:50

Ericson2314 force-pushed the no-dependent-realisations branch from d795f87 to 15f3abb Compare October 23, 2025 16:42

Ericson2314 mentioned this pull request Nov 3, 2025

Split realisation protocol unit tests #14465

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Ericson2314 force-pushed the no-dependent-realisations branch 3 times, most recently from 78329ec to 2f799fe Compare November 6, 2025 18:29

Ericson2314 force-pushed the no-dependent-realisations branch 2 times, most recently from fad08df to 5fed736 Compare November 6, 2025 22:14

Ericson2314 force-pushed the no-dependent-realisations branch 4 times, most recently from aed2570 to 8c3e710 Compare November 21, 2025 05:21

Ericson2314 force-pushed the no-dependent-realisations branch 3 times, most recently from 85ed2a5 to fecd798 Compare November 25, 2025 21:27

Ericson2314 mentioned this pull request Nov 25, 2025

DrvOutputSubstitutionGoal: Don't actually fetch any store objects #14648

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Ericson2314 commented Nov 26, 2025

View reviewed changes

Ericson2314 force-pushed the no-dependent-realisations branch from fecd798 to 0c33c8d Compare December 4, 2025 15:22

Ericson2314 force-pushed the no-dependent-realisations branch 6 times, most recently from 6900a7f to 3986922 Compare December 13, 2025 17:12

Ericson2314 force-pushed the no-dependent-realisations branch from 3986922 to 809bafb Compare December 15, 2025 07:12

Ericson2314 commented Dec 15, 2025

View reviewed changes

Ericson2314 force-pushed the no-dependent-realisations branch from 809bafb to 7e34eea Compare December 17, 2025 00:09

xokdvium reviewed Dec 17, 2025

View reviewed changes

xokdvium approved these changes Dec 17, 2025

View reviewed changes

Ericson2314 force-pushed the no-dependent-realisations branch from 7e34eea to 4a5d960 Compare December 17, 2025 01:13

Ericson2314 enabled auto-merge December 17, 2025 01:14

Ericson2314 added this pull request to the merge queue Dec 17, 2025

Merged via the queue into NixOS:master with commit f536b25 Dec 17, 2025
16 checks passed

Ericson2314 deleted the no-dependent-realisations branch December 17, 2025 02:55

roberth mentioned this pull request Mar 2, 2026

Release notes for 2.34.0 #15363

Merged

brittonr pushed a commit to brittonr/nix that referenced this pull request Apr 1, 2026

Merge pull request NixOS#14247 from obsidiansystems/no-dependent-real…

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…isations Remove dependent realisations

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Remove dependent realisations#14247

Remove dependent realisations#14247
Ericson2314 merged 1 commit intoNixOS:masterfrom
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