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56 lines
3.5 KiB
56 lines
3.5 KiB
Design Architecture for WORM
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This document describes the basic architecture for a DAL and ORM layer.
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This is a general treatment and unfinished.
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The database abstaction layer consists of four functional components that share one point of
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entry to the database (via. the driver).
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1. Classes which offer and API for basic CRUD interaction with the database.
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These include:
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* WSqlDatabase - the sole point of access recommended; all raw/direct interaction with
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the database should use an instance of this class - the API is intended to provide any
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direct query actions, insertions, selection of datasets, etc.
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* WSqlDriver - this is a base class to be implemented by adapters for specific datastore
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engines (currently MySql5, Sqlite3 and PosrgreSQL adapters are implemented). This class
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does all the heavy lifting behind the scenes for the WSqlDatabase API. It should not be
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used directly.
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* WSqlRecord - datasets (or result sets) are encapsulated by WSqlRecord; this class is
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returned by the API for queries that return results (may be empty ..) - it is initialized and
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managed by the driver which hands it to WSqlDatabase. Random access to sets of the
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records is supported (if cached). This is also the prefered method of insertion or update
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- an initialized WSqlRecord sent to the driver is the cleanest interaction.
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WSqlRecord is basically a vector of WSqlFields with some convenience methods for seeking
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in the columns.
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* WSqlField - represents a single data column in a record consisting of a column name
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and a value (ie. simple key/value data structure). It does _not_ contain metadata about
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the value. The value is stored as a string of characters as received from the database.
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The value can therefor be easily converted to native C++ data types using the convenience
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methods provided.
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This class is intended to provide a simple and efficient data transfer - not metadata; if
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metadata about the database column, data type etc. is needed WSqlColumn is to be used.
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* WSqlResult - this class represents a set of returned records (or records to be inserted/updated)
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it is an internal managed cache object for the driver.
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2. Classes which offer and API for obtaining metadata about the database schemata. These may
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instantiated for access to metadata at runtime but are primarily for use by the ORM generator.
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These include:
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* WSqlCatalog - access to all schemata in the DBMS (unimplemented)
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* WSqlSchema - access to a metadata for a single database
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* WSqlTable - metadata for a single table
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* WSqlColumn - metadata for a single column
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* WSqlIndex - metadata for an index in a table
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* WSqlForiegnKey - metadata for a foriegn key relationship
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3. Classes which deal with generating ORM class object source code representing the metadata
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for existing database schemata.
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These include:
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* TBD
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4. Generated ORM classes and scaffolding providing an alternate CRUD vector. These class
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object may be used directly for CRUD functions with no interaction with the DAL classes.
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Eg.:
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user = new User(); user->setName("joe"); user->save();
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or
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int id = 33; user = User::load(id); cout << user->name();
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