A few new explanations.
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@ -63,6 +63,7 @@ GROFF = groff $(GROFF_OPTS)
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$(SRC).pdf:
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$(SOELIM) < $(SRC).ms |\
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./bin/utf8-to-ms.sh |\
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$(PRECONV) |\
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$(EQN) |\
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$(GHIGHLIGHT) |\
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@ -140,8 +140,15 @@ legal_symbols() sed \
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-e "s/c2 ae/5c 5b 72 67 5d/g"\
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-e "s/e2 84 a2/5c 5b 74 6d 5d/g"
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# TODO: ├─│└
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misc() sed \
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-e "s/e2 94 9c/+/g"\
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-e "s/e2 94 80/-/g"\
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-e "s/e2 94 82/|/g"\
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-e 's/e2 94 94/+/g'
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hexutf8_to_hexms() {
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text_markers | accents | ligatures | legal_symbols
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text_markers | accents | ligatures | legal_symbols | misc
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}
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to_hex_one_column | regroup_lines | hexutf8_to_hexms | from_hex
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108
graphs/graphs.ms
108
graphs/graphs.ms
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@ -53,14 +53,17 @@ which points to entries in the "movie" table.
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.UL "The SQL language"
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enables arbitrary operations on databases: add, search, modify and delete entries.
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Furthermore, SQL also enables to manage administrative operations of the databases themselves: creating databases and tables, managing users with fine-grained authorizations, etc.
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This language is used in applications to perform operations on the database, binding the code with the database.
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SQL is used between the application and the database, to perform operations and to provide results when due.
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SQL is also used
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.UL outside
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the application, by admins for managing databases and potentially by some technical users to retrieve some data without a dedicated interface\*[*].
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the application, by admins for managing databases and potentially by some
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.I non-developer
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users to retrieve some data without a dedicated interface\*[*].
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.FOOTNOTE1
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One of the first objectives of SQL was to enable a class of
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.I non-developer
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users to talk directly to the database so they can access the data without bothering the developers.
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This has value for many companies and organizations.
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.FOOTNOTE2
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Many tools were used or even developed over the years specifically to aleviate the inherent complexity and limitations of SQL.
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@ -71,7 +74,7 @@ thus, SQL databases can be scripted to automate operations and provide a massive
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.I "stored procedures" , (
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see
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.I "PL/SQL" ).
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Writing SQL requests requires a lot of boiletplate since there is no integration in the programming languages, leading to multiple function calls for any operation on the database;
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Writing SQL requests requires a lot of boilerplate since there is no integration in the programming languages, leading to multiple function calls for any operation on the database;
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thus, object-relational mapping (ORM) libraries were created to reduce the massive code duplication.
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And so on.
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@ -103,18 +106,102 @@ Since homogeneity is not necessary anymore, databases have fewer (or different)
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Document-oriented databases are a sub-class of key-value stores, where metadata can be extracted from the entries for further optimizations.
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And that's exactly what is being done in Document Oriented DataBase (DODB).
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Contrary to SQL, DODB has a very narrow scope: to provide a library enabling to store, retrieve, modify and delete data.
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.UL "Contrary to SQL" ,
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DODB has a very narrow scope: to provide a library enabling to store, retrieve, modify and delete data.
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In this way, DODB transforms any application in a database manager.
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DODB doesn't provide an interactive shell, there is no request language to perform arbitrary operations on the database, no statistical optimizations of the requests based on query frequencies, etc.
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Instead, DODB reduces the complexity of the infrastructure, stores data in plain files and enables simple manual scripting with widespread unix tools.
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Simplicity is key.
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.UL "Contrary to other NoSQL databases" ,
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DODB doesn't provide an application but a library, nothing else.
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The idea is to help developers to store their data themselves, not depending on
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. I yet-another-all-in-one
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massive tool.
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The library writes (and removes) data on a storage device, has a few retrieval and update mechanisms and that's it\*[*].
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.FOOTNOTE1
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The lack of features
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.I is
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the feature.
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Even with that motto, the tool still is expected to be convenient for most applications.
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.FOOTNOTE2
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This document will provide an extensive documentation on how DODB works and how to use it.
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Limitations are also clearly stated in a dedicated section.
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A few experiments are described to provide an overview of the performance you can expect from this approach.
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Finally, a conclusion is drawn based on a real-world usage of this library.
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.
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.SECTION Basic usage
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.
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.SECTION How DODB works
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DODB is a hash table.
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The key of the hash is an auto-incremented number, the value is the stored data.
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The following section will explain the file-system representation of the data and the very few added mechanisms to speed-up searches.
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.SS Storing data
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When a value is added, it is serialized\*[*] and written in a dedicated file.
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.FOOTNOTE1
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Serialization is currently in JSON.
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CBOR is a work-in-progress.
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Nothing binds DODB to a particular format.
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.FOOTNOTE2
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The key of the hash is a number, auto-incremented, used as the name of the stored file.
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The following example shows the content of the file system after adding three values.
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.de TREE1
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.QP
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.KS
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.ft CW
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.nf
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..
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.de TREE2
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.ft
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.fi
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.KE
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.QE
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..
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.TREE1
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$ tree storage/
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storage
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`-- data
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+-- 0000000000
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+-- 0000000001
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`-- 0000000002
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.TREE2
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In this example, the directory
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.I storage/data
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contains all three serialized values, with a formated number as their file name.
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.SS Indexes
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Database entries can be
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.I indexed
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based on their attributes.
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There are currently three main ways to search a value by its attributes: basic indexes, partitions and tags.
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.SSS Basic indexes (1 to 1 relation)
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Basic indexes represent one-to-one relations, such as an index in SQL.
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For example, in a database of
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.I cars ,
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each car can have a dedicted (unique) name.
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This
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.I name
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attribute can be used to speed-up searches.
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On the file-system, this will be translated as this:
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.TREE1
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storage
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+-- data
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| `-- 0000000000
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`-- indexes
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`-- by_name
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`-- Ford C-MAX -> ../../data/0000000000
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.TREE2
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As shown, the file "Ford C-MAX" is a symbolic link to a data file.
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The name of the symlink file has been extracted from the value itself, enabling to list all the cars and their names with a simple
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.UL ls
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in the
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.I storage/indexes/by_name/
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directory.
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.TBD
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.SECTION Basic usage of the DODB library
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.TBD
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.SECTION A few more options
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.
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.TBD
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.SECTION Limits of DODB
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.
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.TBD
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.SECTION Experimental scenario
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.LP
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The following experiment shows the performance of DODB based on quering durations.
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@ -211,3 +298,8 @@ Caching the value enables a massive performance gain, data can be retrieved seve
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.SS Tags (n to n relations)
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.LP
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.so graph_query_tag.grap
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.
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.SECTION Future work
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.TBD
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.SECTION Conclusion
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.TBD
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@ -4,6 +4,7 @@
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.nr FM 0.3i \" page foot margin default 1i
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.nr DI 0
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.nr FF 3 \" footnotes' type: numbered, with point, indented
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.nr PS 12
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.
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.nr LIST_NUMBER 0 +1
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.
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@ -398,8 +399,9 @@ Compilé pour la dernière fois le
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\\$*
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.ds LH \\$*
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.de HD .XX
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.sp -2.8
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\l'7.5i'
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.sp -2.3
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.nr LINEWIDTH (\n[LL]/1.0i)
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\l'\\\\n[LINEWIDTH]i'
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.sp +1.5
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.br
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..XX
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