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Avoid value_for_database if attribute not updated
After a record is saved, `ActiveModel::Attribute#forgetting_assignment`
is called on each of its attributes. `forgetting_assignment`, in turn,
calls `ActiveModel::Attribute#value_for_database`. If an attribute was
not updated, and therefore `value_for_database` was not previously
computed, this will involve an unnecessary serialize (and cast,
depending on type). And if the attribute was not previously read, it
will also involve an unnecessary deserialize (and cast, depending on
type).
This commit overrides `FromDatabase#forgetting_assignment` to dup the
attribute instead of computing `value_for_database` in the case where
the attribute was not updated. This can improve the performance for
basic types:
**Benchmark script**
```ruby
# frozen_string_literal: true
require "benchmark/ips"
ActiveModel::Attribute.alias_method :baseline_forgetting_assignment, :forgetting_assignment
{
big_integer: 123456,
boolean: 1,
date: "1999-12-31",
datetime: "1999-12-31 12:34:56.789011",
decimal: 123.456,
float: 123.456,
immutable_string: "abcdef",
integer: 123456,
string: "abcdef",
time: "1999-12-31 12:34:56.789011",
}.each do |type_name, value_before_type_cast|
puts "=== #{type_name} ".ljust(70, "=")
type = ActiveModel::Type.lookup(type_name)
Benchmark.ips do |x|
x.report("before") do
attribute = ActiveModel::Attribute.from_database("x", value_before_type_cast, type)
attribute.baseline_forgetting_assignment
end
x.report("after") do
attribute = ActiveModel::Attribute.from_database("x", value_before_type_cast, type)
attribute.forgetting_assignment
end
x.compare!
end
Benchmark.ips do |x|
x.report("before w/ read") do
attribute = ActiveModel::Attribute.from_database("x", value_before_type_cast, type)
attribute.value
attribute.baseline_forgetting_assignment
end
x.report("after w/ read") do
attribute = ActiveModel::Attribute.from_database("x", value_before_type_cast, type)
attribute.value
attribute.forgetting_assignment
end
x.compare!
end
end
```
**Results**
```
=== big_integer ======================================================
Warming up --------------------------------------
before 35.830k i/100ms
after 99.520k i/100ms
Calculating -------------------------------------
before 356.010k (± 1.0%) i/s - 1.792M in 5.032655s
after 989.674k (± 1.2%) i/s - 4.976M in 5.028638s
Comparison:
after: 989674.2 i/s
before: 356010.4 i/s - 2.78x (± 0.00) slower
Warming up --------------------------------------
before w/ read 35.030k i/100ms
after w/ read 56.005k i/100ms
Calculating -------------------------------------
before w/ read 349.509k (± 1.3%) i/s - 1.752M in 5.012188s
after w/ read 558.953k (± 1.2%) i/s - 2.800M in 5.010511s
Comparison:
after w/ read: 558953.4 i/s
before w/ read: 349508.6 i/s - 1.60x (± 0.00) slower
=== boolean ==========================================================
Warming up --------------------------------------
before 31.989k i/100ms
after 99.698k i/100ms
Calculating -------------------------------------
before 319.969k (± 1.0%) i/s - 1.631M in 5.099207s
after 994.759k (± 1.1%) i/s - 4.985M in 5.011775s
Comparison:
after: 994758.6 i/s
before: 319969.3 i/s - 3.11x (± 0.00) slower
Warming up --------------------------------------
before w/ read 31.090k i/100ms
after w/ read 33.306k i/100ms
Calculating -------------------------------------
before w/ read 308.859k (± 1.1%) i/s - 1.554M in 5.033639s
after w/ read 332.726k (± 1.1%) i/s - 1.665M in 5.005669s
Comparison:
after w/ read: 332726.2 i/s
before w/ read: 308858.6 i/s - 1.08x (± 0.00) slower
=== date =============================================================
Warming up --------------------------------------
before 14.466k i/100ms
after 98.451k i/100ms
Calculating -------------------------------------
before 145.594k (± 1.4%) i/s - 737.766k in 5.068354s
after 990.526k (± 1.1%) i/s - 5.021M in 5.069638s
Comparison:
after: 990526.4 i/s
before: 145593.9 i/s - 6.80x (± 0.00) slower
Warming up --------------------------------------
before w/ read 14.130k i/100ms
after w/ read 14.702k i/100ms
Calculating -------------------------------------
before w/ read 141.887k (± 1.3%) i/s - 720.630k in 5.079719s
after w/ read 148.244k (± 1.0%) i/s - 749.802k in 5.058433s
Comparison:
after w/ read: 148244.1 i/s
before w/ read: 141886.8 i/s - 1.04x (± 0.00) slower
=== datetime =========================================================
Warming up --------------------------------------
before 9.484k i/100ms
after 97.889k i/100ms
Calculating -------------------------------------
before 95.640k (± 1.3%) i/s - 483.684k in 5.058190s
after 988.827k (± 1.1%) i/s - 4.992M in 5.049376s
Comparison:
after: 988827.4 i/s
before: 95639.7 i/s - 10.34x (± 0.00) slower
Warming up --------------------------------------
before w/ read 9.440k i/100ms
after w/ read 10.479k i/100ms
Calculating -------------------------------------
before w/ read 94.420k (± 1.1%) i/s - 481.440k in 5.099530s
after w/ read 105.935k (± 1.0%) i/s - 534.429k in 5.045377s
Comparison:
after w/ read: 105935.2 i/s
before w/ read: 94419.6 i/s - 1.12x (± 0.00) slower
=== decimal ==========================================================
Warming up --------------------------------------
before 12.877k i/100ms
after 98.081k i/100ms
Calculating -------------------------------------
before 127.627k (± 1.4%) i/s - 643.850k in 5.045749s
after 990.178k (± 0.9%) i/s - 5.002M in 5.052175s
Comparison:
after: 990178.0 i/s
before: 127627.5 i/s - 7.76x (± 0.00) slower
Warming up --------------------------------------
before w/ read 12.640k i/100ms
after w/ read 19.739k i/100ms
Calculating -------------------------------------
before w/ read 124.933k (± 1.4%) i/s - 632.000k in 5.059694s
after w/ read 200.110k (± 1.0%) i/s - 1.007M in 5.031169s
Comparison:
after w/ read: 200110.3 i/s
before w/ read: 124932.8 i/s - 1.60x (± 0.00) slower
=== float ============================================================
Warming up --------------------------------------
before 45.424k i/100ms
after 99.512k i/100ms
Calculating -------------------------------------
before 449.861k (± 1.0%) i/s - 2.271M in 5.049231s
after 991.130k (± 1.1%) i/s - 4.976M in 5.020705s
Comparison:
after: 991130.0 i/s
before: 449861.3 i/s - 2.20x (± 0.00) slower
Warming up --------------------------------------
before w/ read 43.283k i/100ms
after w/ read 42.888k i/100ms
Calculating -------------------------------------
before w/ read 431.630k (± 1.0%) i/s - 2.164M in 5.014423s
after w/ read 429.631k (± 1.0%) i/s - 2.187M in 5.091609s
Comparison:
before w/ read: 431630.0 i/s
after w/ read: 429631.0 i/s - same-ish: difference falls within error
=== immutable_string =================================================
Warming up --------------------------------------
before 36.820k i/100ms
after 97.812k i/100ms
Calculating -------------------------------------
before 369.412k (± 1.1%) i/s - 1.878M in 5.083860s
after 985.345k (± 1.1%) i/s - 4.988M in 5.063224s
Comparison:
after: 985345.0 i/s
before: 369411.8 i/s - 2.67x (± 0.00) slower
Warming up --------------------------------------
before w/ read 36.082k i/100ms
after w/ read 37.250k i/100ms
Calculating -------------------------------------
before w/ read 361.134k (± 1.0%) i/s - 1.840M in 5.096085s
after w/ read 369.471k (± 0.8%) i/s - 1.862M in 5.041349s
Comparison:
after w/ read: 369471.0 i/s
before w/ read: 361133.6 i/s - 1.02x (± 0.00) slower
=== integer ==========================================================
Warming up --------------------------------------
before 35.763k i/100ms
after 98.444k i/100ms
Calculating -------------------------------------
before 358.171k (± 1.1%) i/s - 1.824M in 5.092870s
after 995.138k (± 1.0%) i/s - 5.021M in 5.045729s
Comparison:
after: 995137.6 i/s
before: 358171.4 i/s - 2.78x (± 0.00) slower
Warming up --------------------------------------
before w/ read 34.534k i/100ms
after w/ read 53.971k i/100ms
Calculating -------------------------------------
before w/ read 345.029k (± 1.0%) i/s - 1.727M in 5.005030s
after w/ read 537.373k (± 0.9%) i/s - 2.699M in 5.022178s
Comparison:
after w/ read: 537373.4 i/s
before w/ read: 345029.3 i/s - 1.56x (± 0.00) slower
=== string ===========================================================
Warming up --------------------------------------
before 33.882k i/100ms
after 97.193k i/100ms
Calculating -------------------------------------
before 339.174k (± 1.1%) i/s - 1.728M in 5.095272s
after 984.544k (± 0.9%) i/s - 4.957M in 5.035057s
Comparison:
after: 984543.5 i/s
before: 339174.0 i/s - 2.90x (± 0.00) slower
Warming up --------------------------------------
before w/ read 32.897k i/100ms
after w/ read 31.767k i/100ms
Calculating -------------------------------------
before w/ read 329.911k (± 0.8%) i/s - 1.678M in 5.085756s
after w/ read 320.010k (± 0.6%) i/s - 1.620M in 5.062867s
Comparison:
before w/ read: 329910.6 i/s
after w/ read: 320010.1 i/s - 1.03x (± 0.00) slower
=== time =============================================================
Warming up --------------------------------------
before 7.461k i/100ms
after 97.467k i/100ms
Calculating -------------------------------------
before 74.854k (± 1.5%) i/s - 380.511k in 5.084475s
after 986.169k (± 0.9%) i/s - 4.971M in 5.040923s
Comparison:
after: 986168.8 i/s
before: 74854.5 i/s - 13.17x (± 0.00) slower
Warming up --------------------------------------
before w/ read 7.438k i/100ms
after w/ read 8.046k i/100ms
Calculating -------------------------------------
before w/ read 73.436k (± 1.5%) i/s - 371.900k in 5.065491s
after w/ read 79.752k (± 1.5%) i/s - 402.300k in 5.045612s
Comparison:
after w/ read: 79751.7 i/s
before w/ read: 73435.8 i/s - 1.09x (± 0.00) slower
```
And, notably, this avoids potentially expensive serialize and
deserialize calls for non-basic types, such as with encrypted
attributes, when the attribute has not been read or assigned:
**Before**
```irb
irb> Post.encrypts :body, encryptor: MyLoggingEncryptor.new
irb> post = Post.create!(title: "untitled", body: "The Body")
! encrypting "The Body"
TRANSACTION (0.1ms) begin transaction
Post Create (0.6ms) INSERT INTO "posts" ...
! decrypted "The Body"
TRANSACTION (120.2ms) commit transaction
irb> post.update!(title: "The Title")
TRANSACTION (0.1ms) begin transaction
Post Update (0.7ms) UPDATE "posts" ...
! decrypted "The Body"
! encrypting "The Body"
TRANSACTION (92.1ms) commit transaction
```
**After**
```irb
irb> Post.encrypts :body, encryptor: MyLoggingEncryptor.new
irb> post = Post.create!(title: "untitled", body: "The Body")
! encrypting "The Body"
TRANSACTION (0.1ms) begin transaction
Post Create (0.7ms) INSERT INTO "posts" ...
! decrypted "The Body"
TRANSACTION (103.7ms) commit transaction
irb> post.update!(title: "The Title")
TRANSACTION (0.1ms) begin transaction
Post Update (0.7ms) UPDATE "posts" ...
TRANSACTION (91.2ms) commit transaction
```
This commit is contained in:
Jonathan Hefner
parent
6676989957
commit
98aa59a7f6
1 changed files with 13 additions and 0 deletions
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@ -175,6 +175,19 @@ module ActiveModel
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type.deserialize(value)
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end
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def forgetting_assignment
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# If this attribute was not persisted (with a `value_for_database`
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# that might differ from `value_before_type_cast`) and `value` has not
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# changed in place, we can simply dup this attribute to avoid
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# deserialize / cast / serialize calls from computing the new
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# attribute's `value_before_type_cast`.
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if !defined?(@value_for_database) && !changed_in_place?
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dup
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else
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super
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end
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end
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private
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def _original_value_for_database
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value_before_type_cast
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