lix/src/libstore/ca-specific-schema.sql
Sergei Trofimovich 975b0b52e7 ca: add sqlite index on RealisationsRefs(realisationReference)
Without the change any CA deletion triggers linear scan on large
RealisationsRefs table:

    sqlite>.eqp full
    sqlite> delete from RealisationsRefs where realisationReference IN ( select id from Realisations where outputPath = 1234567890 );
    QUERY PLAN
    |--SCAN RealisationsRefs
    `--LIST SUBQUERY 1
       `--SEARCH Realisations USING COVERING INDEX IndexRealisationsRefsOnOutputPath (outputPath=?)

With the change it gets turned into a lookup:

    sqlite> CREATE INDEX IndexRealisationsRefsRealisationReference on RealisationsRefs(realisationReference);
    sqlite> delete from RealisationsRefs where realisationReference IN ( select id from Realisations where outputPath = 1234567890 );
    QUERY PLAN
    |--SEARCH RealisationsRefs USING INDEX IndexRealisationsRefsRealisationReference (realisationReference=?)
    `--LIST SUBQUERY 1
       `--SEARCH Realisations USING COVERING INDEX IndexRealisationsRefsOnOutputPath (outputPath=?)
2022-04-21 10:06:39 +02:00

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-- Extension of the sql schema for content-addressed derivations.
-- Won't be loaded unless the experimental feature `ca-derivations`
-- is enabled
create table if not exists Realisations (
id integer primary key autoincrement not null,
drvPath text not null,
outputName text not null, -- symbolic output id, usually "out"
outputPath integer not null,
signatures text, -- space-separated list
foreign key (outputPath) references ValidPaths(id) on delete cascade
);
create index if not exists IndexRealisations on Realisations(drvPath, outputName);
-- We can end-up in a weird edge-case where a path depends on itself because
-- its an output of a CA derivation, that happens to be the same as one of its
-- dependencies.
-- In that case we have a dependency loop (path -> realisation1 -> realisation2
-- -> path) that we need to break by removing the dependencies between the
-- realisations
create trigger if not exists DeleteSelfRefsViaRealisations before delete on ValidPaths
begin
delete from RealisationsRefs where realisationReference in (
select id from Realisations where outputPath = old.id
);
end;
create table if not exists RealisationsRefs (
referrer integer not null,
realisationReference integer,
foreign key (referrer) references Realisations(id) on delete cascade,
foreign key (realisationReference) references Realisations(id) on delete restrict
);
-- used by deletion trigger
create index if not exists IndexRealisationsRefsRealisationReference on RealisationsRefs(realisationReference);
-- used by QueryRealisationReferences
create index if not exists IndexRealisationsRefs on RealisationsRefs(referrer);
-- used by cascade deletion when ValidPaths is deleted
create index if not exists IndexRealisationsRefsOnOutputPath on Realisations(outputPath);