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Last annex: add a few details about the API.

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Philippe Pittoli 2025-04-21 03:08:19 +02:00
parent 7cf7104757
commit 6cb42f9953
1 changed files with 47 additions and 1 deletions

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@ -2001,7 +2001,23 @@ cars_by_keywords = cars.new_tags "keywords", &.keywords
cars_by_keywords = cars.new_RAM_tags "keywords", &.keywords
.SOURCE
.QE
.
For any trigger, in case some entries do not have the indexed value, the user-provided function has to return a
.dq NoIndex
value.
.QP
.SOURCE Ruby ps=9 vs=10
# In case some values do not have a color or shouldn't be indexed for
# some reason. Works the same for basic indexes and tags.
cars_by_color = cars.new_partition "color", do |car|
if color = car.color
color
else
DODB.no_index
end
end
.SOURCE
.QE
.
.SS Data retrieval, update and deletion with an attribute (index, partition, tags)
.
@ -2042,6 +2058,8 @@ Partitions and tags can take a block of code to narrow the selection.
.SOURCE Ruby ps=9 vs=10
cars_by_name.delete "Corvet" # Deletes the car named "Corvet".
cars_by_color.delete "red" # Deletes all red cars.
cars_by_color.delete? "yellow" # Deletes yellow cars, if any (no MissingEntry
# exception).
# Deletes cars that are both slow and expensive.
cars_by_keywords.delete ["slow", "expensive"]
@ -2063,9 +2081,11 @@ end
The Tag index enables to search for a value based on multiple keys.
For example, searching for all cars that are both fast and elegant can be written this way:
.QP
.KS
.SOURCE Ruby ps=9 vs=10
fast_elegant_cars = cars_by_keywords.get ["fast", "elegant"]
.SOURCE
.KE
Used with a list of keys, the
.FUNCTION_CALL get
function returns an empty list in case the search failed.
@ -2073,3 +2093,29 @@ function returns an empty list in case the search failed.
The implementation was designed to be simple (7 lines of code), not efficient.
However, with data and index caches, the search is expected to meet about everyone's requirements, speed-wise, given that the tags are small enough (a few thousand entries).
.QE
.
.SSS reindex
The database can regenerate its indexes at any time by using the
.I reindex_everything!
function which removes all indexes (including the filesystem representation) then sets off all the triggers to index the values again.
.QP
.SOURCE Ruby ps=9 vs=10
cars.reindex_everything!
.SOURCE
Reindexing can be used after restoring a database backup which didn't include the filesystem representation.
Moreover, values could be re-indexed once a new trigger has been introduced.
For example, the database is created and some values are added, but the admin wants a new index and all previously added values must be indexed (as new values) to keep the index consistent.
.QE
.
.SS Unsafe operations
By default, adding or removing a value in the database is thread-safe (thanks to a file-based locking mechanism).
In case there is no need for thread-safe operations:
.
.QP
.SOURCE Ruby ps=9 vs=10
cars.unsafe_add new_car
cars.unsafe_delete key
.SOURCE
Unsafe operations on the database.
.QE