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A few minor modifications to the paper.

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Philippe PITTOLI 2024-05-22 19:24:19 +02:00
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1 changed files with 26 additions and 5 deletions
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@ -290,13 +290,23 @@ attribute can be used to speed-up searches.
cars_by_name = cars.new_index "name", do |car| cars_by_name = cars.new_index "name", do |car|
car.name car.name
end end
# Two other ways to say the same thing, thanks to the Crystal syntax:
cars_by_name = cars.new_index "name", { |car| car.name }
cars_by_name = cars.new_index "name", &.name
.SOURCE .SOURCE
Once the index has been created, every added or modified entry in the database will be indexed. Once the index has been created, every added or modified entry in the database will be indexed.
Adding an index (basic index, partition or tag) provides an object used to manipulate the database based on this index. Adding an index (basic index, partition or tag) provides an
.I object
used to manipulate the database based on this index.
Let's call it an Let's call it an
.I "index object" . .I "index object" .
In the code above, the
.I "index object"
is named
.I "cars_by_name" .
.QE .QE
.
The The
.I "index object" .I "index object"
has several useful functions. has several useful functions.
@ -311,7 +321,6 @@ cars_by_name.update "Corvet", new_car
# In case the index hasn't changed (the name attribute in this example), # In case the index hasn't changed (the name attribute in this example),
# the update can be even simpler. # the update can be even simpler.
new_car = Car.new "Corvet", "green", ["eco-friendly"]
cars_by_name.update new_car cars_by_name.update new_car
# Delete the car named "Corvet". # Delete the car named "Corvet".
@ -354,6 +363,9 @@ attribute of our cars.
cars_by_color = database.new_partition "color", do |car| cars_by_color = database.new_partition "color", do |car|
car.color car.color
end end
# Shortcut:
cars_by_color = database.new_partition "color", &.color
.SOURCE .SOURCE
.QE .QE
As with basic indexes, once the partition is asked to the database, every new or modified entry will be indexed. As with basic indexes, once the partition is asked to the database, every new or modified entry will be indexed.
@ -396,6 +408,9 @@ Tags are basically partitions but the indexed attribute can have multiple values
cars_by_keywords = database.new_tags "keywords", do |car| cars_by_keywords = database.new_tags "keywords", do |car|
car.keywords car.keywords
end end
# Shortcut:
cars_by_keywords = database.new_tags "keywords", &.keywords
.SOURCE .SOURCE
As with other indexes, once the tag is requested to the database, every new or modified entry will be indexed. As with other indexes, once the tag is requested to the database, every new or modified entry will be indexed.
.QE .QE
@ -464,9 +479,9 @@ A cached database has the same API as the other DODB databases.
database = DODB::Storage::Cached(Car).new "path/to/db-cars" database = DODB::Storage::Cached(Car).new "path/to/db-cars"
.SOURCE .SOURCE
All operations of the All operations of the
.CLASS DODB::Storage::Basic .CLASS Storage::Basic
class are available for class are available for
.CLASS DODB::Storage::Cached . .CLASS Storage::Cached .
.QE .QE
. .
.SS Cached indexes .SS Cached indexes
@ -844,7 +859,9 @@ In our example, each \f[CW]car\f[] has an unique \fIname\f[] which is used as an
The following graph represents the result of 100 queries of a car based on its name. The following graph represents the result of 100 queries of a car based on its name.
The experiment starts with a database containing 1,000 cars and goes up to 250,000 cars. The experiment starts with a database containing 1,000 cars and goes up to 250,000 cars.
.ps -2
.so graph_query_index.grap .so graph_query_index.grap
.ps \n[PS]
Since there is only one value to retrieve, the request is quick and time is almost constant. Since there is only one value to retrieve, the request is quick and time is almost constant.
When the value and the index are kept in memory (see \f[CW]RAM only\f[] and \f[CW]Cached db\f[]), the retrieval is almost instantaneous (about 50 to 120 ns). When the value and the index are kept in memory (see \f[CW]RAM only\f[] and \f[CW]Cached db\f[]), the retrieval is almost instantaneous (about 50 to 120 ns).
@ -879,11 +896,15 @@ Caching the value enables a massive performance gain, data can be retrieved seve
.SS Partitions (1 to n relations) .SS Partitions (1 to n relations)
.LP .LP
.ps -2
.so graph_query_partition.grap .so graph_query_partition.grap
.ps \n[PS]
.SS Tags (n to n relations) .SS Tags (n to n relations)
.LP .LP
.ps -2
.so graph_query_tag.grap .so graph_query_tag.grap
.ps \n[PS]
. .
. .
. .