Rails 5.2 cache key for relations generating two queries

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 Nov 10 at 10:08

asked Nov 9 at 8:59

gingerlime

2,99932456

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 Nov 10 at 10:08

asked Nov 9 at 8:59

gingerlime

2,99932456

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 Nov 10 at 10:08

asked Nov 9 at 8:59

gingerlime

2,99932456

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 Nov 10 at 10:08

asked Nov 9 at 8:59

gingerlime

2,99932456

edited Nov 10 at 10:08

asked Nov 9 at 8:59

gingerlime

2,99932456

edited Nov 10 at 10:08

asked Nov 9 at 8:59

gingerlime

2,99932456

asked Nov 9 at 8:59

gingerlime

2,99932456

asked Nov 9 at 8:59

gingerlime

2,99932456

add a comment |

active

oldest

votes

Your Answer

StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});

}
});

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53222582%2frails-5-2-cache-key-for-relations-generating-two-queries%23new-answer', 'question_page');
}
);

Post as a guest

Name

Required, but never shown

active

oldest

votes

draft saved

draft discarded

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Name

Required, but never shown

Name

Required, but never shown

This page is only for reference, If you need detailed information, please check here

搜尋此網誌

Agfdhyk