Class Amalgalite::Database
In: lib/amalgalite/database.rb
lib/amalgalite/database.rb
Parent: Object

The encapsulation of a connection to an SQLite3 database.

Example opening and possibly creating a new database

  db = Amalgalite::Database.new( "mydb.db" )
  db.execute( "SELECT * FROM table" ) do |row|
    puts row
  end

  db.close

Open a database read only:

  db = Amalgalite::Database.new( "mydb.db", "r" )

Open an in-memory database:

  db = Amalgalite::MemoryDatabase.new

Methods

aggregate   aggregate   autocommit?   autocommit?   busy_handler   busy_handler   clear_taps!   clear_taps!   close   close   commit   commit   deferred_transaction   deferred_transaction   define_aggregate   define_aggregate   define_busy_handler   define_busy_handler   define_function   define_function   define_progress_handler   define_progress_handler   encoding   encoding   escape   escape   exclusive_transaction   exclusive_transaction   execute   execute   execute_batch   execute_batch   first_row_from   first_row_from   first_value_from   first_value_from   function   function   immediate_transaction   immediate_transaction   import_csv_to_table   import_csv_to_table   in_transaction?   in_transaction?   interrupt!   interrupt!   last_insert_rowid   last_insert_rowid   new   new   open?   open?   pragma   pragma   prepare   prepare   profile_tap=   profile_tap=   progress_handler   progress_handler   quote   quote   release   release   reload_schema!   reload_schema!   remove_aggregate   remove_aggregate   remove_busy_handler   remove_busy_handler   remove_function   remove_function   remove_progress_handler   remove_progress_handler   replicate_to   replicate_to   rollback   rollback   rollback_to   rollback_to   row_changes   row_changes   savepoint   savepoint   schema   schema   total_changes   total_changes   trace_tap=   trace_tap=   transaction   transaction   type_map=   type_map=   utf16?   utf16?  

Included Modules

Amalgalite::SQLite3::Constants Amalgalite::SQLite3::Constants

Classes and Modules

Class Amalgalite::Database::AggregateError
Class Amalgalite::Database::BusyHandlerError
Class Amalgalite::Database::FunctionError
Class Amalgalite::Database::InvalidModeError
Class Amalgalite::Database::ProgressHandlerError
Class Amalgalite::Database::TransactionBehavior

Constants

VALID_MODES = { "r" => Open::READONLY, "r+" => Open::READWRITE, "w+" => Open::READWRITE | Open::CREATE, }   list of valid modes for opening an Amalgalite::Database
VALID_MODES = { "r" => Open::READONLY, "r+" => Open::READWRITE, "w+" => Open::READWRITE | Open::CREATE, }   list of valid modes for opening an Amalgalite::Database

Attributes

aggregates  [R]  A list of the user defined aggregates
aggregates  [R]  A list of the user defined aggregates
api  [R]  the low level Amalgalite::SQLite3::Database
api  [R]  the low level Amalgalite::SQLite3::Database
functions  [R]  A list of the user defined functions
functions  [R]  A list of the user defined functions
profile_tap  [R]  An object that follows the ProfileTap protocol, or nil. By default this is nil
profile_tap  [R]  An object that follows the ProfileTap protocol, or nil. By default this is nil
trace_tap  [R]  An object that follows the TraceTap protocol, or nil. By default this is nil
trace_tap  [R]  An object that follows the TraceTap protocol, or nil. By default this is nil
type_map  [R]  An object that follows the TypeMap protocol, or nil. By default this is an instances of TypeMaps::DefaultMap
type_map  [R]  An object that follows the TypeMap protocol, or nil. By default this is an instances of TypeMaps::DefaultMap

Public Class methods

Create a new Amalgalite database

The first parameter is the filename of the sqlite database. Specifying ":memory:" as the filename creates an in-memory database.

The second parameter is the standard file modes of how to open a file.

The modes are:

  • r - Read-only
  • r+ - Read/write, an error is thrown if the database does not already exist
  • w+ - Read/write, create a new database if it doesn‘t exist

w+ is the default as this is how most databases will want to be utilized.

opts is a hash of available options for the database:

  • :utf16 option to set the database to a utf16 encoding if creating a database.

By default, databases are created with an encoding of utf8. Setting this to true and opening an already existing database has no effect.

NOTE Currently :utf16 is not supported by Amalgalite, it is planned for a later release

Create a new Amalgalite database

The first parameter is the filename of the sqlite database. Specifying ":memory:" as the filename creates an in-memory database.

The second parameter is the standard file modes of how to open a file.

The modes are:

  • r - Read-only
  • r+ - Read/write, an error is thrown if the database does not already exist
  • w+ - Read/write, create a new database if it doesn‘t exist

w+ is the default as this is how most databases will want to be utilized.

opts is a hash of available options for the database:

  • :utf16 option to set the database to a utf16 encoding if creating a database.

By default, databases are created with an encoding of utf8. Setting this to true and opening an already existing database has no effect.

NOTE Currently :utf16 is not supported by Amalgalite, it is planned for a later release

Public Instance methods

aggregate( name, klass )

Alias for define_aggregate

aggregate( name, klass )

Alias for define_aggregate

Is the database in autocommit mode or not

Is the database in autocommit mode or not

busy_handler( callable = nil, &block )
busy_handler( callable = nil, &block )

clear all the current taps

clear all the current taps

Close the database

Close the database

deferred_transaction( mode = TransactionBehavior::DEFERRED, &block )

Alias for transaction

deferred_transaction( mode = TransactionBehavior::DEFERRED, &block )

Alias for transaction

Define an SQL aggregate function, these are functions like max(), min(), avg(), etc. SQL functions that would be used when a GROUP BY clause is in effect. See also ::Amalgalite::Aggregate.

A new instance of MyAggregateClass is created for each instance that the SQL aggregate is mentioned in SQL.

Define an SQL aggregate function, these are functions like max(), min(), avg(), etc. SQL functions that would be used when a GROUP BY clause is in effect. See also ::Amalgalite::Aggregate.

A new instance of MyAggregateClass is created for each instance that the SQL aggregate is mentioned in SQL.

Register a busy handler for this database connection, the handler MUST follow the to_proc protocol indicating that is will +respond_to?(:call)+. This is intrinsic to lambdas and blocks so those will work automatically.

This exposes the sqlite busy handler api to ruby.

The busy handler‘s _call(N)_ method may be invoked whenever an attempt is made to open a database table that another thread or process has locked. N will be the number of times the _call(N)_ method has been invoked during this locking event.

The handler may or maynot be called based upon what SQLite determins.

If the handler returns nil or false then no more busy handler calls will be made in this lock event and you are probably going to see an SQLite::Error in your immediately future in another process or in another piece of code.

If the handler returns non-nil or non-false then another attempt will be made to obtain the lock, lather, rinse, repeat.

If an Exception happens in a busy handler, it will be the same as if the busy handler had returned nil or false. The exception itself will not be propogated further.

Register a busy handler for this database connection, the handler MUST follow the to_proc protocol indicating that is will +respond_to?(:call)+. This is intrinsic to lambdas and blocks so those will work automatically.

This exposes the sqlite busy handler api to ruby.

The busy handler‘s _call(N)_ method may be invoked whenever an attempt is made to open a database table that another thread or process has locked. N will be the number of times the _call(N)_ method has been invoked during this locking event.

The handler may or maynot be called based upon what SQLite determins.

If the handler returns nil or false then no more busy handler calls will be made in this lock event and you are probably going to see an SQLite::Error in your immediately future in another process or in another piece of code.

If the handler returns non-nil or non-false then another attempt will be made to obtain the lock, lather, rinse, repeat.

If an Exception happens in a busy handler, it will be the same as if the busy handler had returned nil or false. The exception itself will not be propogated further.

register a callback to be exposed as an SQL function. There are multiple ways to register this function:

  1. db.function( "name" ) { |a| … }
    • pass function a name and a block.
    • The SQL function name taking arity parameters will be registered, where arity is the arity of the block.
    • The return value of the block is the return value of the registred SQL function
  2. db.function( "name", callable )
    • pass function a name and something that responds_to?( :to_proc )
    • The SQL function name is registered taking arity parameters is registered where arity is the arity of +callable.to_proc.call+
    • The return value of the +callable.to_proc.call+ is the return value of the SQL function

See also ::Amalgalite::Function

register a callback to be exposed as an SQL function. There are multiple ways to register this function:

  1. db.function( "name" ) { |a| … }
    • pass function a name and a block.
    • The SQL function name taking arity parameters will be registered, where arity is the arity of the block.
    • The return value of the block is the return value of the registred SQL function
  2. db.function( "name", callable )
    • pass function a name and something that responds_to?( :to_proc )
    • The SQL function name is registered taking arity parameters is registered where arity is the arity of +callable.to_proc.call+
    • The return value of the +callable.to_proc.call+ is the return value of the SQL function

See also ::Amalgalite::Function

Register a progress handler for this database connection, the handler MUST follow the to_proc protocol indicating that is will +respond_to?(:call)+. This is intrinsic to lambdas and blocks so those will work automatically.

This exposes the sqlite progress handler api to ruby.

The progress handler‘s _call()_ method may be invoked ever N SQLite op codes. If the progress handler returns anything that can evaluate to true then current running sqlite statement is terminated at the earliest oppportunity.

You can use this to be notified that a thread is still processingn a request.

Register a progress handler for this database connection, the handler MUST follow the to_proc protocol indicating that is will +respond_to?(:call)+. This is intrinsic to lambdas and blocks so those will work automatically.

This exposes the sqlite progress handler api to ruby.

The progress handler‘s _call()_ method may be invoked ever N SQLite op codes. If the progress handler returns anything that can evaluate to true then current running sqlite statement is terminated at the earliest oppportunity.

You can use this to be notified that a thread is still processingn a request.

return the encoding of the database

return the encoding of the database

SQL escape the input string

SQL escape the input string

Execute a single SQL statement.

If called with a block and there are result rows, then they are iteratively yielded to the block.

If no block is passed, then all the results are returned as an arrayfields instance. This is an array with field name access.

If no block is passed, and there are no results, then an empty Array is returned.

On an error an exception is thrown

This is just a wrapper around the preparation of an Amalgalite Statement and iterating over the results.

Execute a single SQL statement.

If called with a block and there are result rows, then they are iteratively yielded to the block.

If no block is passed, then all the results are returned as an arrayfields instance. This is an array with field name access.

If no block is passed, and there are no results, then an empty Array is returned.

On an error an exception is thrown

This is just a wrapper around the preparation of an Amalgalite Statement and iterating over the results.

Execute a batch of statements, this will execute all the sql in the given string until no more sql can be found in the string. It will bind the same parameters to each statement. All data that would be returned from all of the statements is thrown away.

All statements to be executed in the batch must be terminated with a ’;’ Returns the number of statements executed

Execute a batch of statements, this will execute all the sql in the given string until no more sql can be found in the string. It will bind the same parameters to each statement. All data that would be returned from all of the statements is thrown away.

All statements to be executed in the batch must be terminated with a ’;’ Returns the number of statements executed

Execute a sql statment, and only return the first row of results. This is a shorthand method when you only want a single row of results from a query. If there is no result, then return an empty array

It is in all other was, exactly like execute()

Execute a sql statment, and only return the first row of results. This is a shorthand method when you only want a single row of results from a query. If there is no result, then return an empty array

It is in all other was, exactly like execute()

Execute an sql statement, and return only the first column of the first row. If there is no result, return nil.

It is in all other ways, exactly like first_row_from()

Execute an sql statement, and return only the first column of the first row. If there is no result, return nil.

It is in all other ways, exactly like first_row_from()

function( name, callable = nil, &block )

Alias for define_function

function( name, callable = nil, &block )

Alias for define_function

import_csv_to_table() takes 2 required arguments, and a hash of options. The first argument is the path to a CSV, the second is the table in which to load the data. The options has is a subset of those used by CSV

  • :col_sep - the string placed between each field. Default is ","
  • :row_sep - the String appended to the end of each row. Default is :auto
  • :quote_char - The character used to quote fields. Default ’"’
  • :headers - set to true or :first_row if there are headers in this CSV. Default is false.
               This may also be an Array.  If that is the case then the
               array is used as the fields in the CSV and the fields in the
               table in which to insert.  If this is set to an Array, it is
               assumed that all rows in the csv will be inserted.
    

import_csv_to_table() takes 2 required arguments, and a hash of options. The first argument is the path to a CSV, the second is the table in which to load the data. The options has is a subset of those used by CSV

  • :col_sep - the string placed between each field. Default is ","
  • :row_sep - the String appended to the end of each row. Default is :auto
  • :quote_char - The character used to quote fields. Default ’"’
  • :headers - set to true or :first_row if there are headers in this CSV. Default is false.
               This may also be an Array.  If that is the case then the
               array is used as the fields in the CSV and the fields in the
               table in which to insert.  If this is set to an Array, it is
               assumed that all rows in the csv will be inserted.
    

return whether or not the database is currently in a transaction or not

return whether or not the database is currently in a transaction or not

Cause another thread with a handle on this database to be interrupted and return at the earliest opportunity as interrupted. It is not safe to call this method if the database might be closed before interrupt! returns.

Cause another thread with a handle on this database to be interrupted and return at the earliest opportunity as interrupted. It is not safe to call this method if the database might be closed before interrupt! returns.

Return the rowid of the last inserted row

Return the rowid of the last inserted row

Is the database open or not

Is the database open or not

Run a pragma command against the database

Returns the result set of the pragma

Run a pragma command against the database

Returns the result set of the pragma

Prepare a statement for execution

If called with a block, the statement is yielded to the block and the statement is closed when the block is done.

 db.prepare( "SELECT * FROM table WHERE c = ?" ) do |stmt|
   list_of_c_values.each do |c|
     stmt.execute( c ) do |row|
       puts "when c = #{c} : #{row.inspect}"
     end
   end
 end

Or without a block:

  stmt = db.prepare( "INSERT INTO t1(x, y, z) VALUES ( :

Prepare a statement for execution

If called with a block, the statement is yielded to the block and the statement is closed when the block is done.

 db.prepare( "SELECT * FROM table WHERE c = ?" ) do |stmt|
   list_of_c_values.each do |c|
     stmt.execute( c ) do |row|
       puts "when c = #{c} : #{row.inspect}"
     end
   end
 end

Or without a block:

  stmt = db.prepare( "INSERT INTO t1(x, y, z) VALUES ( :

Register a profile tap.

Registering a profile tap means that the obj registered will have its profile method called with an Integer and a String parameter every time a profile event happens. The Integer is the number of nanoseconds it took for the String (SQL) to execute in wall-clock time.

That is, every time a profile event happens in SQLite the following is invoked:

  obj.profile( str, int )

For instance:

  db.profile_tap = Amalgalite::ProfileTap.new( logger, 'debug' )

This will register an instance of ProfileTap, which wraps an logger object. On each profile event the ProfileTap#profile method will be called which in turn will call <tt>logger.debug<tt> with a formatted string containing the String and Integer from the profile event.

  db.profile_tap = nil

This will unregister the profile tap

Register a profile tap.

Registering a profile tap means that the obj registered will have its profile method called with an Integer and a String parameter every time a profile event happens. The Integer is the number of nanoseconds it took for the String (SQL) to execute in wall-clock time.

That is, every time a profile event happens in SQLite the following is invoked:

  obj.profile( str, int )

For instance:

  db.profile_tap = Amalgalite::ProfileTap.new( logger, 'debug' )

This will register an instance of ProfileTap, which wraps an logger object. On each profile event the ProfileTap#profile method will be called which in turn will call <tt>logger.debug<tt> with a formatted string containing the String and Integer from the profile event.

  db.profile_tap = nil

This will unregister the profile tap

progress_handler( op_code_count = 25, callable = nil, &block )
progress_handler( op_code_count = 25, callable = nil, &block )

Surround the give string with single-quotes and escape any single-quotes in the string

Surround the give string with single-quotes and escape any single-quotes in the string

Release a savepoint. This is similar to a commit but only for savepoints. All savepoints up the savepoint stack and include the name savepoint being released are ‘committed’ to the transaction. There are several ways of thinking about release and they are all detailed in the sqlite documentation: sqlite.org/lang_savepoint.html

Release a savepoint. This is similar to a commit but only for savepoints. All savepoints up the savepoint stack and include the name savepoint being released are ‘committed’ to the transaction. There are several ways of thinking about release and they are all detailed in the sqlite documentation: sqlite.org/lang_savepoint.html

By default once the schema is obtained, it is cached. This is here to force the schema to be reloaded.

By default once the schema is obtained, it is cached. This is here to force the schema to be reloaded.

Remove an aggregate from use in the database. Since the same aggregate may be refistered more than once with different arity, you may specify the arity, or the aggregate class, or nil. If nil is used for the arity then Amalgalite does its best to remove all aggregates of the given name

Remove an aggregate from use in the database. Since the same aggregate may be refistered more than once with different arity, you may specify the arity, or the aggregate class, or nil. If nil is used for the arity then Amalgalite does its best to remove all aggregates of the given name

Remove the busy handler for this database connection.

Remove the busy handler for this database connection.

Remove a function from use in the database. Since the same function may be registered more than once with different arity, you may specify the arity, or the function object, or nil. If nil is used for the arity, then Amalgalite does its best to remove all functions of given name.

Remove a function from use in the database. Since the same function may be registered more than once with different arity, you may specify the arity, or the function object, or nil. If nil is used for the arity, then Amalgalite does its best to remove all functions of given name.

Remove the progress handler for this database connection.

Remove the progress handler for this database connection.

replicate_to() takes a single argument, either a String or an Amalgalite::Database. It returns the replicated database object. If given a String, it will truncate that database if it already exists.

Replicate the current database to another location, this can be used for a number of purposes:

  • load an sqlite database from disk into memory
  • snaphost an in memory db and save it to disk
  • backup on sqlite database to another location

replicate_to() takes a single argument, either a String or an Amalgalite::Database. It returns the replicated database object. If given a String, it will truncate that database if it already exists.

Replicate the current database to another location, this can be used for a number of purposes:

  • load an sqlite database from disk into memory
  • snaphost an in memory db and save it to disk
  • backup on sqlite database to another location

Rollback to a savepoint. The transaction is not cancelled, the transaction is restarted.

Rollback to a savepoint. The transaction is not cancelled, the transaction is restarted.

return how many rows changed in the last insert, update or delete statement.

return how many rows changed in the last insert, update or delete statement.

Much of the following documentation is para-phrased from sqlite.org/lang_savepoint.html

Savepoints are a method of creating transactions, similar to transaction except that they may be nested.

  • Every savepoint must have a name, to_s is called on the method argument
  • A savepoint does not need to be initialized inside a transaction. If it is not inside a transaction it behaves exactly as if a DEFERRED transaction had been started.
  • If a block is passed to saveponit then when the block exists, it is guaranteed that either a ‘RELEASE’ or ‘ROLLBACK TO name’ has been executed.
  • If any exception happens during the savepoint transaction, then a ‘ROLLOBACK TO’ is issued when the block closes.
  • If no exception happens during the transaction then a ‘RELEASE name’ is issued upon leaving the block

If no block is passed in then you are on your own.

Much of the following documentation is para-phrased from sqlite.org/lang_savepoint.html

Savepoints are a method of creating transactions, similar to transaction except that they may be nested.

  • Every savepoint must have a name, to_s is called on the method argument
  • A savepoint does not need to be initialized inside a transaction. If it is not inside a transaction it behaves exactly as if a DEFERRED transaction had been started.
  • If a block is passed to saveponit then when the block exists, it is guaranteed that either a ‘RELEASE’ or ‘ROLLBACK TO name’ has been executed.
  • If any exception happens during the savepoint transaction, then a ‘ROLLOBACK TO’ is issued when the block closes.
  • If no exception happens during the transaction then a ‘RELEASE name’ is issued upon leaving the block

If no block is passed in then you are on your own.

Returns a Schema object containing the table and column structure of the database.

Returns a Schema object containing the table and column structure of the database.

return how many rows have changed since this connection to the database was opened.

return how many rows have changed since this connection to the database was opened.

Register a trace tap.

Registering a trace tap measn that the obj registered will have its trace method called with a string parameter at various times. If the object doesn‘t respond to the trace method then write will be called.

For instance:

  db.trace_tap = Amalgalite::TraceTap.new( logger, 'debug' )

This will register an instance of TraceTap, which wraps an logger object. On each trace event the TraceTap#trace method will be called, which in turn will call the logger.debug method

  db.trace_tap = $stderr

This will register the $stderr io stream as a trace tap. Every time a trace event happens then $stderr.write( msg ) will be called.

  db.trace_tap = nil

This will unregistere the trace tap

Register a trace tap.

Registering a trace tap measn that the obj registered will have its trace method called with a string parameter at various times. If the object doesn‘t respond to the trace method then write will be called.

For instance:

  db.trace_tap = Amalgalite::TraceTap.new( logger, 'debug' )

This will register an instance of TraceTap, which wraps an logger object. On each trace event the TraceTap#trace method will be called, which in turn will call the logger.debug method

  db.trace_tap = $stderr

This will register the $stderr io stream as a trace tap. Every time a trace event happens then $stderr.write( msg ) will be called.

  db.trace_tap = nil

This will unregistere the trace tap

Begin a transaction. The valid transaction types are:

DEFERRED:no read or write locks are created until the first statement is executed that requries a read or a write
IMMEDIATE:a readlock is obtained immediately so that no other process can write to the database
EXCLUSIVE:a read+write lock is obtained, no other proces can read or write to the database

As a convenience, these are constants available in the Database::TransactionBehavior class.

Amalgalite Transactions are database level transactions, just as SQLite‘s are.

If a block is passed in, then when the block exits, it is guaranteed that either ‘COMMIT’ or ‘ROLLBACK’ has been executed.

If any exception happens during the transaction that is caught by Amalgalite, then a ‘ROLLBACK’ is issued when the block closes.

If no exception happens during the transaction then a ‘COMMIT’ is issued upon leaving the block.

If no block is passed in then you are on your own.

Nesting a transaaction via the transaction method are no-ops. If you call transaction within a transaction, no new transaction is started, the current one is just continued.

True nexted transactions are available through the savepoint method.

Begin a transaction. The valid transaction types are:

DEFERRED:no read or write locks are created until the first statement is executed that requries a read or a write
IMMEDIATE:a readlock is obtained immediately so that no other process can write to the database
EXCLUSIVE:a read+write lock is obtained, no other proces can read or write to the database

As a convenience, these are constants available in the Database::TransactionBehavior class.

Amalgalite Transactions are database level transactions, just as SQLite‘s are.

If a block is passed in, then when the block exits, it is guaranteed that either ‘COMMIT’ or ‘ROLLBACK’ has been executed.

If any exception happens during the transaction that is caught by Amalgalite, then a ‘ROLLBACK’ is issued when the block closes.

If no exception happens during the transaction then a ‘COMMIT’ is issued upon leaving the block.

If no block is passed in then you are on your own.

Nesting a transaaction via the transaction method are no-ops. If you call transaction within a transaction, no new transaction is started, the current one is just continued.

True nexted transactions are available through the savepoint method.

Assign your own TypeMap instance to do type conversions. The value assigned here must respond to bind_type_of and result_value_of methods. See the TypeMap class for more details.

Assign your own TypeMap instance to do type conversions. The value assigned here must respond to bind_type_of and result_value_of methods. See the TypeMap class for more details.

Is the database utf16 or not? A database is utf16 if the encoding is not UTF-8. Database can only be UTF-8 or UTF-16, and the default is UTF-8

Is the database utf16 or not? A database is utf16 if the encoding is not UTF-8. Database can only be UTF-8 or UTF-16, and the default is UTF-8

[Validate]