The Database class encapsulates a single connection to a SQLite database. Its usage is very straightforward:
require 'sqlite' db = SQLite::Database.new( "data.db" ) db.execute( "select * from table" ) do |row| p row end db.close
It wraps the lower-level methods provides by the API module, include includes the Pragmas module for access to various pragma convenience methods.
The Database class provides type translation services as well, by which the SQLite data types (which are all represented as strings) may be converted into their corresponding types (as defined in the schemas for their tables). This translation only occurs when querying data from the database—insertions and updates are all still typeless.
Furthermore, the Database class has been designed to work well with the ArrayFields module from Ara Howard. If you require the ArrayFields module before performing a query, and if you have not enabled results as hashes, then the results will all be indexible by field name.
- busy_handler
- busy_timeout
- changes
- close
- closed?
- commit
- complete?
- create_aggregate
- create_aggregate_handler
- create_function
- decode
- encode
- execute
- execute2
- execute_batch
- get_first_row
- get_first_value
- interrupt
- last_insert_row_id
- new
- open
- prepare
- query
- quote
- rollback
- transaction
- transaction_active?
- translator
- type_translation
- type_translation=
[R] | handle | The low-level opaque database handle that this object wraps. |
[RW] | results_as_hash | A boolean that indicates whether rows in result sets should be returned as hashes or not. By default, rows are returned as arrays. |
Return true if the string is a valid (ie, parsable) SQL statement, and false otherwise.
[ show source ]
# File lib/sqlite/database.rb, line 99 99: def self.complete?( string ) 100: SQLite::API.complete( string ) 101: end
Unserializes the object contained in the given string. The string must be one that was returned by encode.
[ show source ]
# File lib/sqlite/database.rb, line 93 93: def self.decode( string ) 94: Marshal.load( Base64.decode64( string ) ) 95: end
Returns a string that represents the serialization of the given object. The string may safely be used in an SQL statement.
[ show source ]
# File lib/sqlite/database.rb, line 87 87: def self.encode( object ) 88: Base64.encode64( Marshal.dump( object ) ).strip 89: end
Create a new Database object that opens the given file. The mode parameter has no meaning yet, and may be omitted. If the file does not exist, it will be created if possible.
By default, the new database will return result rows as arrays (results_as_hash) and has type translation disabled (type_translation=).
[ show source ]
# File lib/sqlite/database.rb, line 116 116: def initialize( file_name, mode=0 ) 117: @handle = SQLite::API.open( file_name, mode ) 118: @closed = false 119: @results_as_hash = false 120: @type_translation = false 121: @translator = nil 122: end
Opens the database contained in the given file. This just calls new, passing 0 as the mode parameter. This returns the new Database instance.
[ show source ]
# File lib/sqlite/database.rb, line 74 74: def self.open( file_name ) 75: new( file_name, 0 ) 76: end
Quotes the given string, making it safe to use in an SQL statement. It replaces all instances of the single-quote character with two single-quote characters. The modified string is returned.
[ show source ]
# File lib/sqlite/database.rb, line 81 81: def self.quote( string ) 82: string.gsub( /'/, "''" ) 83: end
Register a busy handler with this database instance. When a requested resource is busy, this handler will be invoked. If the handler returns false, the operation will be aborted; otherwise, the resource will be requested again.
The handler will be invoked with the name of the resource that was busy, and the number of times it has been retried.
See also busy_timeout.
[ show source ]
# File lib/sqlite/database.rb, line 307 307: def busy_handler( &block ) # :yields: resource, retries 308: SQLite::API.busy_handler( @handle, block ) 309: end
Indicates that if a request for a resource terminates because that resource is busy, SQLite should wait for the indicated number of milliseconds before trying again. By default, SQLite does not retry busy resources. To restore the default behavior, send 0 as the ms parameter.
See also busy_handler.
[ show source ]
# File lib/sqlite/database.rb, line 318 318: def busy_timeout( ms ) 319: SQLite::API.busy_timeout( @handle, ms ) 320: end
Returns the number of changes made to this database instance by the last operation performed. Note that a "delete from table" without a where clause will not affect this value.
[ show source ]
# File lib/sqlite/database.rb, line 289 289: def changes 290: SQLite::API.changes( @handle ) 291: end
Closes this database. No checks are done to ensure that a database is not closed more than once, and closing a database more than once can be catastrophic.
[ show source ]
# File lib/sqlite/database.rb, line 148 148: def close 149: SQLite::API.close( @handle ) 150: @closed = true 151: end
Returns true if this database instance has been closed (see close).
[ show source ]
# File lib/sqlite/database.rb, line 154 154: def closed? 155: @closed 156: end
Commits the current transaction. If there is no current transaction, this will cause an error to be raised. This returns true, in order to allow it to be used in idioms like abort? and rollback or commit.
[ show source ]
# File lib/sqlite/database.rb, line 593 593: def commit 594: execute "commit transaction" 595: @transaction_active = false 596: true 597: end
Creates a new aggregate function for use in SQL statements. Aggregate functions are functions that apply over every row in the result set, instead of over just a single row. (A very common aggregate function is the "count" function, for determining the number of rows that match a query.)
The new function will be added as name, with the given arity. (For variable arity functions, use -1 for the arity.) If type is non-nil, it should be a value as described in create_function.
The step parameter must be a proc object that accepts as its first parameter a FunctionProxy instance (representing the function invocation), with any subsequent parameters (up to the function’s arity). The step callback will be invoked once for each row of the result set.
The finalize parameter must be a proc object that accepts only a single parameter, the FunctionProxy instance representing the current function invocation. It should invoke FunctionProxy#set_result to store the result of the function.
Example:
step = proc do |func, value| func[ :total ] ||= 0 func[ :total ] += ( value ? value.length : 0 ) end finalize = proc do |func| func.set_result( func[ :total ] || 0 ) end db.create_aggregate( "lengths", 1, step, finalize, :numeric ) puts db.get_first_value( "select lengths(name) from table" )
See also create_aggregate_handler for a more object-oriented approach to aggregate functions.
[ show source ]
# File lib/sqlite/database.rb, line 411 411: def create_aggregate( name, arity, step, finalize, type=nil ) 412: case type 413: when :numeric 414: type = SQLite::API::NUMERIC 415: when :text 416: type = SQLite::API::TEXT 417: when :args 418: type = SQLite::API::ARGS 419: end 420: 421: step_callback = proc do |func,*args| 422: ctx = SQLite::API.aggregate_context( func ) 423: unless ctx[:__error] 424: begin 425: step.call( FunctionProxy.new( func, ctx ), *args ) 426: rescue Exception => e 427: ctx[:__error] = e 428: end 429: end 430: end 431: 432: finalize_callback = proc do |func| 433: ctx = SQLite::API.aggregate_context( func ) 434: unless ctx[:__error] 435: begin 436: finalize.call( FunctionProxy.new( func, ctx ) ) 437: rescue Exception => e 438: SQLite::API.set_result_error( func, "#{e.message} (#{e.class})" ) 439: end 440: else 441: e = ctx[:__error] 442: SQLite::API.set_result_error( func, "#{e.message} (#{e.class})" ) 443: end 444: end 445: 446: SQLite::API.create_aggregate( @handle, name, arity, 447: step_callback, finalize_callback ) 448: 449: SQLite::API.function_type( @handle, name, type ) if type 450: 451: self 452: end
This is another approach to creating an aggregate function (see create_aggregate). Instead of explicitly specifying the name, callbacks, arity, and type, you specify a factory object (the "handler") that knows how to obtain all of that information. The handler should respond to the following messages:
function_type: | corresponds to the type parameter of create_aggregate. This is an optional message, and if the handler does not respond to it, the function type will not be set for this function. |
arity: | corresponds to the arity parameter of create_aggregate. This message is optional, and if the handler does not respond to it, the function will have an arity of -1. |
name: | this is the name of the function. The handler must implement this message. |
new: | this must be implemented by the handler. It should return a new instance of the object that will handle a specific invocation of the function. |
The handler instance (the object returned by the new message, described above), must respond to the following messages:
step: | this is the method that will be called for each step of the aggregate function’s evaluation. It should implement the same signature as the step callback for create_aggregate. |
finalize: | this is the method that will be called to finalize the aggregate function’s evaluation. It should implement the same signature as the finalize callback for create_aggregate. |
Example:
class LengthsAggregateHandler def self.function_type; :numeric; end def self.arity; 1; end def initialize @total = 0 end def step( ctx, name ) @total += ( name ? name.length : 0 ) end def finalize( ctx ) ctx.set_result( @total ) end end db.create_aggregate_handler( LengthsAggregateHandler ) puts db.get_first_value( "select lengths(name) from A" )
[ show source ]
# File lib/sqlite/database.rb, line 505 505: def create_aggregate_handler( handler ) 506: type = nil 507: arity = -1 508: 509: type = handler.function_type if handler.respond_to?(:function_type) 510: arity = handler.arity if handler.respond_to?(:arity) 511: name = handler.name 512: 513: case type 514: when :numeric 515: type = SQLite::API::NUMERIC 516: when :text 517: type = SQLite::API::TEXT 518: when :args 519: type = SQLite::API::ARGS 520: end 521: 522: step = proc do |func,*args| 523: ctx = SQLite::API.aggregate_context( func ) 524: unless ctx[ :__error ] 525: ctx[ :handler ] ||= handler.new 526: begin 527: ctx[ :handler ].step( FunctionProxy.new( func, ctx ), *args ) 528: rescue Exception => e 529: ctx[ :__error ] = e 530: end 531: end 532: end 533: 534: finalize = proc do |func| 535: ctx = SQLite::API.aggregate_context( func ) 536: unless ctx[ :__error ] 537: ctx[ :handler ] ||= handler.new 538: begin 539: ctx[ :handler ].finalize( FunctionProxy.new( func, ctx ) ) 540: rescue Exception => e 541: ctx[ :__error ] = e 542: end 543: end 544: 545: if ctx[ :__error ] 546: e = ctx[ :__error ] 547: SQLite::API.set_result_error( func, "#{e.message} (#{e.class})" ) 548: end 549: end 550: 551: SQLite::API.create_aggregate( @handle, name, arity, step, finalize ) 552: SQLite::API.function_type( @handle, name, type ) if type 553: 554: self 555: end
Creates a new function for use in SQL statements. It will be added as name, with the given arity. (For variable arity functions, use -1 for the arity.) If type is non-nil, it should either be an integer (indicating that the type of the function is always the type of the argument at that index), or one of the symbols :numeric, :text, :args (in which case the function is, respectively, numeric, textual, or the same type as its arguments).
The block should accept at least one parameter—the FunctionProxy instance that wraps this function invocation—and any other arguments it needs (up to its arity).
The block does not return a value directly. Instead, it will invoke the FunctionProxy#set_result method on the func parameter and indicate the return value that way.
Example:
db.create_function( "maim", 1, :text ) do |func, value| if value.nil? func.set_value nil else func.set_value value.split(//).sort.join end end puts db.get_first_value( "select maim(name) from table" )
[ show source ]
# File lib/sqlite/database.rb, line 350 350: def create_function( name, arity, type=nil, &block ) # :yields: func, *args 351: case type 352: when :numeric 353: type = SQLite::API::NUMERIC 354: when :text 355: type = SQLite::API::TEXT 356: when :args 357: type = SQLite::API::ARGS 358: end 359: 360: callback = proc do |func,*args| 361: begin 362: block.call( FunctionProxy.new( func ), *args ) 363: rescue Exception => e 364: SQLite::API.set_result_error( func, "#{e.message} (#{e.class})" ) 365: end 366: end 367: 368: SQLite::API.create_function( @handle, name, arity, callback ) 369: SQLite::API.function_type( @handle, name, type ) if type 370: 371: self 372: end
Executes the given SQL statement. If additional parameters are given, they are treated as bind variables, and are bound to the placeholders in the query.
Each placeholder must match one of the following formats:
- ?
- ?nnn
- :word
- :word:
where nnn is an integer value indicating the index of the bind variable to be bound at that position, and word is an alphanumeric identifier for that placeholder. For "?", an index is automatically assigned of one greater than the previous index used (or 1, if it is the first).
Note that if any of the values passed to this are hashes, then the key/value pairs are each bound separately, with the key being used as the name of the placeholder to bind the value to.
The block is optional. If given, it will be invoked for each row returned by the query. Otherwise, any results are accumulated into an array and returned wholesale.
See also execute2, execute_batch and query for additional ways of executing statements.
[ show source ]
# File lib/sqlite/database.rb, line 191 191: def execute( sql, *bind_vars ) 192: stmt = prepare( sql ) 193: stmt.bind_params( *bind_vars ) 194: result = stmt.execute 195: begin 196: if block_given? 197: result.each { |row| yield row } 198: else 199: return result.inject( [] ) { |arr,row| arr << row; arr } 200: end 201: ensure 202: result.close 203: end 204: end
Executes the given SQL statement, exactly as with execute. However, the first row returned (either via the block, or in the returned array) is always the names of the columns. Subsequent rows correspond to the data from the result set.
Thus, even if the query itself returns no rows, this method will always return at least one row—the names of the columns.
See also execute, execute_batch and query for additional ways of executing statements.
[ show source ]
# File lib/sqlite/database.rb, line 216 216: def execute2( sql, *bind_vars ) 217: stmt = prepare( sql ) 218: stmt.bind_params( *bind_vars ) 219: result = stmt.execute 220: begin 221: if block_given? 222: yield result.columns 223: result.each { |row| yield row } 224: else 225: return result.inject( [ result.columns ] ) { |arr,row| arr << row; arr } 226: end 227: ensure 228: result.close 229: end 230: end
Executes all SQL statements in the given string. By contrast, the other means of executing queries will only execute the first statement in the string, ignoring all subsequent statements. This will execute each one in turn. The same bind parameters, if given, will be applied to each statement.
This always returns nil, making it unsuitable for queries that return rows.
[ show source ]
# File lib/sqlite/database.rb, line 240 240: def execute_batch( sql, *bind_vars ) 241: loop do 242: stmt = prepare( sql ) 243: stmt.bind_params *bind_vars 244: stmt.execute 245: sql = stmt.remainder 246: break if sql.length < 1 247: end 248: nil 249: end
A convenience method for obtaining the first row of a result set, and discarding all others. It is otherwise identical to execute.
See also get_first_value.
[ show source ]
# File lib/sqlite/database.rb, line 265 265: def get_first_row( sql, *bind_vars ) 266: execute( sql, *bind_vars ) { |row| return row } 267: nil 268: end
A convenience method for obtaining the first value of the first row of a result set, and discarding all other values and rows. It is otherwise identical to execute.
See also get_first_row.
[ show source ]
# File lib/sqlite/database.rb, line 275 275: def get_first_value( sql, *bind_vars ) 276: execute( sql, *bind_vars ) { |row| return row[0] } 277: nil 278: end
Interrupts the currently executing operation, causing it to abort.
[ show source ]
# File lib/sqlite/database.rb, line 294 294: def interrupt 295: SQLite::API.interrupt( @handle ) 296: end
Obtains the unique row ID of the last row to be inserted by this Database instance.
[ show source ]
# File lib/sqlite/database.rb, line 282 282: def last_insert_row_id 283: SQLite::API.last_insert_row_id( @handle ) 284: end
Returns a Statement object representing the given SQL. This does not execute the statement; it merely prepares the statement for execution.
[ show source ]
# File lib/sqlite/database.rb, line 160 160: def prepare( sql ) 161: Statement.new( self, sql ) 162: end
This does like execute and execute2 (binding variables and so forth), but instead of yielding each row from the result set, this will yield the ResultSet instance itself (q.v.). If no block is given, the ResultSet instance will be returned.
[ show source ]
# File lib/sqlite/database.rb, line 255 255: def query( sql, *bind_vars, &block ) # :yields: result_set 256: stmt = prepare( sql ) 257: stmt.bind_params( *bind_vars ) 258: stmt.execute( &block ) 259: end
Rolls the current transaction back. If there is no current transaction, this will cause an error to be raised. This returns true, in order to allow it to be used in idioms like abort? and rollback or commit.
[ show source ]
# File lib/sqlite/database.rb, line 603 603: def rollback 604: execute "rollback transaction" 605: @transaction_active = false 606: true 607: end
Begins a new transaction. Note that nested transactions are not allowed by SQLite, so attempting to nest a transaction will result in a runtime exception.
If a block is given, the database instance is yielded to it, and the transaction is committed when the block terminates. If the block raises an exception, a rollback will be performed instead. Note that if a block is given, commit and rollback should never be called explicitly or you’ll get an error when the block terminates.
If a block is not given, it is the caller’s responsibility to end the transaction explicitly, either by calling commit, or by calling rollback.
[ show source ]
# File lib/sqlite/database.rb, line 570 570: def transaction 571: execute "begin transaction" 572: @transaction_active = true 573: 574: if block_given? 575: abort = false 576: begin 577: yield self 578: rescue Exception 579: abort = true 580: raise 581: ensure 582: abort and rollback or commit 583: end 584: end 585: 586: true 587: end
Returns true if there is a transaction active, and false otherwise.
[ show source ]
# File lib/sqlite/database.rb, line 610 610: def transaction_active? 611: @transaction_active 612: end
Return the type translator employed by this database instance. Each database instance has its own type translator; this allows for different type handlers to be installed in each instance without affecting other instances. Furthermore, the translators are instantiated lazily, so that if a database does not use type translation, it will not be burdened by the overhead of a useless type translator. (See the Translator class.)
[ show source ]
# File lib/sqlite/database.rb, line 130 130: def translator 131: @translator ||= Translator.new 132: end
Returns true if type translation is enabled for this database, or false otherwise.
[ show source ]
# File lib/sqlite/database.rb, line 136 136: def type_translation 137: @type_translation 138: end
Enable or disable type translation for this database.
[ show source ]
# File lib/sqlite/database.rb, line 141 141: def type_translation=( mode ) 142: @type_translation = mode 143: end