| Commit message (Collapse) | Author | Age |
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guix_revision_package_derivation_distribution_counts
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To avoid using the old PostgreSQL connection per thread code.
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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.
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That were missing them.
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A large proportion of these changes relate to changing the way
packages relate to derivations. Previously, a package at a given
revision had a single derivation. This was OK, but didn't account for
multiple architectures.
Therefore, these changes mean that a package has multiple derivations,
depending on the system of the derivation, and the target system.
There are multiple changes, small and large to the web interface as
well. More pages link to each other, and the visual display has been
improved somewhat.
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