This is mostly a workaround for the occasional problems with the guix-commits
mailing list, as it can break and then the data service doesn't learn about
new revisions until the problem is fixed.
I think it's still a generally good feature though, and allows deploying the
data service without it consuming emails to learn about new revisions, and is
a step towards integrating some kind of way of notifying the data service to
poll.
This might be generally useful, but I've been looking at it as it offers a way
to try and improve query performance when you want to select all the
derivations related to the packages for a revision.
The data looks like this (for a specified system and target):
┌───────┬───────┐
│ level │ count │
├───────┼───────┤
│ 15 │ 2 │
│ 14 │ 3 │
│ 13 │ 3 │
│ 12 │ 3 │
│ 11 │ 14 │
│ 10 │ 25 │
│ 9 │ 44 │
│ 8 │ 91 │
│ 7 │ 1084 │
│ 6 │ 311 │
│ 5 │ 432 │
│ 4 │ 515 │
│ 3 │ 548 │
│ 2 │ 2201 │
│ 1 │ 21162 │
│ 0 │ 22310 │
└───────┴───────┘
Level 0 reflects the number of packages. Level 1 is similar as you have all
the derivations for the package origins. The remaining levels contain less
packages since it's mostly just derivations involved in bootstrapping.
When using a recursive CTE to collect all the derivations, PostgreSQL assumes
that the each derivation has the same number of inputs, and this leads to a
large overestimation of the number of derivations per a revision. This in turn
can lead to PostgreSQL picking a slower way of running the query.
When it's known how many new derivations you should see at each level, it's
possible to inform PostgreSQL this by using LIMIT's at various points in the
query. This reassures the query planner that it's not going to be handling
lots of rows and helps it make better decisions about how to execute the
query.
This will hopefully provide a less expensive way of finding out if a scheduled
build is probably blocked by other builds failing or being canceled.
By working this out when the build events are recieved, it should be more
feasible to include information about whether builds are likely blocked or not
in various places (e.g. revision comparisons).
And create a proper git_branches table in the process.
I'm hoping this will help with slow deletions from the
package_derivations_by_guix_revision_range table in the case where there are
lots of branches, since it'll separate the data for one branch from another.
These migrations will remove the existing data, so
rebuild-package-derivations-table will currently need manually running to
regenerate it.
Start at least looking for package replacements, and storing the
details (particularly the derivation). I'm looking at doing this so that build
servers using the Guix Data Service can build these derivations.
And use it for the systems in the derivations and package derivations tables.
The primary motivation here is to allow quickly working out what systems the
database contains, and having a small table with just the right data seems a
good way to do that.
This means that these derivations are stored, even if a later part of the
process fails. Having the channel instance derivations stored might help work
out why the failure occurred, or better display information about it.
It has a lot of rows, and this seems to help the query planning for
select-required-builds-that-failed, as I think it helps PostgreSQL better
estimate the row counts that different parts of the query will produce.
This will avoid many queries trying to figure out what the latest build status
is, which will hopefuly simplify queries as well as improving performance.
I've not used these in many places, to try and avoid hiding deleting data, but
in this case, this will allow more easily deleting the derivation source file
nars, by just deleting the derivation_source_files table entry.
Looking at data for the the patches deployment of the Guix Data Service, these
tables look like they might benefit from vacuuming/analyzing more often, so
adjust the configuration so this will hopefully happen.
From the normalized one, to the one actually contained within glibc. Recent
versions of glibc also contain symlinks linking the normalized codeset to the
locales with the .UTF-8 ending, but older ones do not.
Maybe handling codeset normalisation for queries would be good, but the locale
values ending in .UTF-8 are more compatible and allow the code to be
simplified. For querying, maybe there should be a locales table which handles
different representations.
To avoid the index data being too large.
This was first seen in guix commit 1bb4fd64b7bbe5a17eda6f0ca8105283c038f7c8:
psql-query-error (fatal-error PGRES_FATAL_ERROR ERROR: index row size 2808
exceeds maximum 2712 for index "package_descriptions_locale_description_key"
HINT: Values larger than 1/3 of a buffer page cannot be indexed.
Like Cuirass, or the Guix Data Service. This isn't so necessary with Cuirass,
as the derivation/output are unique identifiers, but for the Guix Build
Coordinator, one derivation/output can be built many times, with potentially
differing results.
The Guix Build Coordinator doesn't record timestamps for events
currently. This is something to fix, but allow for build statuses without
timestamps as they're not necessary.
Rather than just the native system. I'm not quite sure of the value here, as I
guess system tests should behave the same regardless of the way the software
is compiled, but this seems like it could be useful, and being explicit about
the system the derivation is for is good.
Stop using the system values as targets, and remove package derivation entries
where this is the case.
Switch the non-cross derivation case to have a target of "", rather than
matching the system, as this makes more sense, and is more consistent now that
the target values no longer match the system values.
Hardcode some more correct target values, and use these instead. Hopefully
this can be better integrated with Guix in the future.
This commit also includes a migration attempting to shrink some indexes.
Christopher Baines
Canan Talayhan
Danjela Lura