Rails 5.2 cache key for relations generating two queries

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I have a view using fragment caching for an ActiveRecord relation, e.g.

<% cache MyModel.all do %>
...
<% end %>

I see two DB queries generated in this case

SELECT COUNT(*) AS "size", MAX("my_model"."updated_at") AS timestamp FROM "my_model"

SELECT "my_model".* from "my_model"

I expect the first one, and it's usually a much more efficient query. I did not expect the second one.

If I instead use:

<% cache ActiveSupport::Cache.expand_cache_key(MyModel.all) do %>
...
<% end %>

then I get only the first query with the same resulting cache key.

Is it a bug or am I doing something wrong?

EDIT: narrowed down to where this happens: see https://github.com/rails/rails/pull/29092#issuecomment-437572543

when
normalize_version
is executed, the relation does not respond to cache_version, and
therefore ends up being expanded with
to_a.
So essentially, calling Product.all.to_a and then for each object
calling cache_version, which returns nil.

edited yesterday

asked 2 days ago

gingerlime

2,99432456

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up vote
1
down vote

favorite

I have a view using fragment caching for an ActiveRecord relation, e.g.

<% cache MyModel.all do %>
...
<% end %>

I see two DB queries generated in this case

SELECT COUNT(*) AS "size", MAX("my_model"."updated_at") AS timestamp FROM "my_model"

SELECT "my_model".* from "my_model"

I expect the first one, and it's usually a much more efficient query. I did not expect the second one.

If I instead use:

<% cache ActiveSupport::Cache.expand_cache_key(MyModel.all) do %>
...
<% end %>

then I get only the first query with the same resulting cache key.

Is it a bug or am I doing something wrong?

EDIT: narrowed down to where this happens: see https://github.com/rails/rails/pull/29092#issuecomment-437572543

when
normalize_version
is executed, the relation does not respond to cache_version, and
therefore ends up being expanded with
to_a.
So essentially, calling Product.all.to_a and then for each object
calling cache_version, which returns nil.

edited yesterday

asked 2 days ago

gingerlime

2,99432456

add a comment |

up vote
1
down vote

favorite

I have a view using fragment caching for an ActiveRecord relation, e.g.

<% cache MyModel.all do %>
...
<% end %>

I see two DB queries generated in this case

SELECT COUNT(*) AS "size", MAX("my_model"."updated_at") AS timestamp FROM "my_model"

SELECT "my_model".* from "my_model"

I expect the first one, and it's usually a much more efficient query. I did not expect the second one.

If I instead use:

<% cache ActiveSupport::Cache.expand_cache_key(MyModel.all) do %>
...
<% end %>

then I get only the first query with the same resulting cache key.

Is it a bug or am I doing something wrong?

EDIT: narrowed down to where this happens: see https://github.com/rails/rails/pull/29092#issuecomment-437572543

when
normalize_version
is executed, the relation does not respond to cache_version, and
therefore ends up being expanded with
to_a.
So essentially, calling Product.all.to_a and then for each object
calling cache_version, which returns nil.

edited yesterday

asked 2 days ago

gingerlime

2,99432456

I have a view using fragment caching for an ActiveRecord relation, e.g.

<% cache MyModel.all do %>
...
<% end %>

I see two DB queries generated in this case

SELECT COUNT(*) AS "size", MAX("my_model"."updated_at") AS timestamp FROM "my_model"

SELECT "my_model".* from "my_model"

I expect the first one, and it's usually a much more efficient query. I did not expect the second one.

If I instead use:

<% cache ActiveSupport::Cache.expand_cache_key(MyModel.all) do %>
...
<% end %>

then I get only the first query with the same resulting cache key.

Is it a bug or am I doing something wrong?

EDIT: narrowed down to where this happens: see https://github.com/rails/rails/pull/29092#issuecomment-437572543

when
normalize_version
is executed, the relation does not respond to cache_version, and
therefore ends up being expanded with
to_a.
So essentially, calling Product.all.to_a and then for each object
calling cache_version, which returns nil.

ruby-on-rails caching activerecord activesupport

edited yesterday

asked 2 days ago

gingerlime

2,99432456

edited yesterday

asked 2 days ago

gingerlime

2,99432456

edited yesterday

asked 2 days ago

gingerlime

2,99432456

asked 2 days ago

gingerlime

2,99432456

asked 2 days ago

gingerlime

2,99432456

add a comment |

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