The Database class encapsulates a single connection to a SQLite3 database. Its usage is very straightforward:
require 'sqlite3' SQLite3::Database.new( "data.db" ) do |db| db.execute( "select * from table" ) do |row| p row end end
It wraps the lower-level methods provides by the selected driver, and includes the Pragmas module for access to various pragma convenience methods.
The Database class provides type translation services as well, by which the SQLite3 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.
A boolean that indicates whether rows in result sets should be returned as hashes or not. By default, rows are returned as arrays.
# File lib/sqlite3/database.rb, line 371 def self.finalize( &block ) define_method(:finalize, &block) end
# File lib/sqlite3/database.rb, line 449 def initialize handler @handler = handler @fp = FunctionProxy.new end
Create a new Database object that opens the
given file. If utf16 is true
, the filename is interpreted as a
UTF-16 encoded string.
By default, the new database will return result rows as arrays (results_as_hash) and has type translation disabled (type_translation=).
static VALUE initialize(int argc, VALUE *argv, VALUE self) { sqlite3RubyPtr ctx; VALUE file; VALUE opts; VALUE zvfs; int mode = SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE; int status; Data_Get_Struct(self, sqlite3Ruby, ctx); rb_scan_args(argc, argv, "12", &file, &opts, &zvfs); #if defined StringValueCStr StringValuePtr(file); rb_check_safe_obj(file); #else Check_SafeStr(file); #endif if(NIL_P(opts)) opts = rb_hash_new(); else Check_Type(opts, T_HASH); #ifdef HAVE_RUBY_ENCODING_H if(UTF16_LE_P(file)) { status = sqlite3_open16(utf16_string_value_ptr(file), &ctx->db); } else { #endif if(Qtrue == rb_hash_aref(opts, sym_utf16)) { status = sqlite3_open16(utf16_string_value_ptr(file), &ctx->db); } else { #ifdef HAVE_RUBY_ENCODING_H if(!UTF8_P(file)) { file = rb_str_export_to_enc(file, rb_utf8_encoding()); } #endif if (Qtrue == rb_hash_aref(opts, ID2SYM(rb_intern("readonly")))) { mode = SQLITE_OPEN_READONLY; } status = sqlite3_open_v2( StringValuePtr(file), &ctx->db, mode, NIL_P(zvfs) ? NULL : StringValuePtr(zvfs) ); } #ifdef HAVE_RUBY_ENCODING_H } #endif CHECK(ctx->db, status) rb_iv_set(self, "@tracefunc", Qnil); rb_iv_set(self, "@authorizer", Qnil); rb_iv_set(self, "@encoding", Qnil); rb_iv_set(self, "@busy_handler", Qnil); rb_iv_set(self, "@collations", rb_hash_new()); rb_iv_set(self, "@functions", rb_hash_new()); rb_iv_set(self, "@results_as_hash", rb_hash_aref(opts, sym_results_as_hash)); rb_iv_set(self, "@type_translation", rb_hash_aref(opts, sym_type_translation)); rb_iv_set(self, "@readonly", mode == SQLITE_OPEN_READONLY ? Qtrue : Qfalse); if(rb_block_given_p()) { rb_yield(self); rb_funcall(self, rb_intern("close"), 0); } return self; }
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.
# File lib/sqlite3/database.rb, line 47 def quote( string ) string.gsub( %r'/, "''" ) end
# File lib/sqlite3/database.rb, line 367 def self.step( &block ) define_method(:step, &block) 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 the mutually exclusive busy_timeout.
static VALUE busy_handler(int argc, VALUE *argv, VALUE self) { sqlite3RubyPtr ctx; VALUE block; int status; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); rb_scan_args(argc, argv, "01", &block); if(NIL_P(block) && rb_block_given_p()) block = rb_block_proc(); rb_iv_set(self, "@busy_handler", block); status = sqlite3_busy_handler( ctx->db, NIL_P(block) ? NULL : rb_sqlite3_busy_handler, (void *)self); CHECK(ctx->db, status); return self; }
Indicates that if a request for a resource terminates because that resource
is busy, SQLite should sleep and retry for up to the indicated number of
milliseconds. By default, SQLite does not retry busy resources. To restore
the default behavior, send 0 as the ms
parameter.
See also the mutually exclusive busy_handler.
static VALUE set_busy_timeout(VALUE self, VALUE timeout) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); CHECK(ctx->db, sqlite3_busy_timeout(ctx->db, (int)NUM2INT(timeout))); return self; }
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.
static VALUE changes(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); return INT2NUM(sqlite3_changes(ctx->db)); }
Closes this database.
static VALUE sqlite3_rb_close(VALUE self) { sqlite3RubyPtr ctx; sqlite3 * db; Data_Get_Struct(self, sqlite3Ruby, ctx); db = ctx->db; CHECK(db, sqlite3_close(ctx->db)); ctx->db = NULL; return self; }
Returns true
if this database instance has been closed (see close).
static VALUE closed_p(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); if(!ctx->db) return Qtrue; return Qfalse; }
Add a collation with name name
, and a comparator
object. The comparator
object should implement a method
called "compare" that takes two parameters and returns an integer less
than, equal to, or greater than 0.
static VALUE collation(VALUE self, VALUE name, VALUE comparator) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); CHECK(ctx->db, sqlite3_create_collation_v2( ctx->db, StringValuePtr(name), SQLITE_UTF8, (void *)comparator, NIL_P(comparator) ? NULL : rb_comparator_func, NULL)); /* Make sure our comparator doesn't get garbage collected. */ rb_hash_aset(rb_iv_get(self, "@collations"), name, comparator); return self; }
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
.
# File lib/sqlite3/database.rb, line 505 def commit execute "commit transaction" true end
Return true
if the string is a valid (ie, parsable) SQL
statement, and false
otherwise.
static VALUE complete_p(VALUE UNUSED(self), VALUE sql) { if(sqlite3_complete(StringValuePtr(sql))) return Qtrue; return Qfalse; }
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.)
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 SQLite3::Database::FunctionProxy#result
to store the result of the function.
Example:
db.create_aggregate( "lengths", 1 ) do step do |func, value| func[ :total ] ||= 0 func[ :total ] += ( value ? value.length : 0 ) end finalize do |func| func.result = func[ :total ] || 0 end end puts db.get_first_value( "select lengths(name) from table" )
See also create_aggregate_handler for a more object-oriented approach to aggregate functions.
# File lib/sqlite3/database.rb, line 363 def create_aggregate( name, arity, step=nil, finalize=nil, text_rep=Constants::TextRep::ANY, &block ) factory = Class.new do def self.step( &block ) define_method(:step, &block) end def self.finalize( &block ) define_method(:finalize, &block) end end if block_given? factory.instance_eval(&block) else factory.class_eval do define_method(:step, step) define_method(:finalize, finalize) end end proxy = factory.new proxy.extend(Module.new { attr_accessor :ctx def step( *args ) super(@ctx, *args) end def finalize super(@ctx) end }) proxy.ctx = FunctionProxy.new define_aggregator(name, proxy) 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:
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.arity; 1; end def initialize @total = 0 end def step( ctx, name ) @total += ( name ? name.length : 0 ) end def finalize( ctx ) ctx.result = @total end end db.create_aggregate_handler( LengthsAggregateHandler ) puts db.get_first_value( "select lengths(name) from A" )
# File lib/sqlite3/database.rb, line 447 def create_aggregate_handler( handler ) proxy = Class.new do def initialize handler @handler = handler @fp = FunctionProxy.new end def step( *args ) @handler.step(@fp, *args) end def finalize @handler.finalize @fp @fp.result end end define_aggregator(handler.name, proxy.new(handler.new)) self 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.)
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 SQLite3::Database::FunctionProxy#result
method on the func
parameter and indicate the return value
that way.
Example:
db.create_function( "maim", 1 ) do |func, value| if value.nil? func.result = nil else func.result = value.split(%r/).sort.join end end puts db.get_first_value( "select maim(name) from table" )
# File lib/sqlite3/database.rb, line 318 def create_function name, arity, text_rep=Constants::TextRep::ANY, &block define_function(name) do |*args| fp = FunctionProxy.new block.call(fp, *args) fp.result end self end
Define an aggregate function named name
using the object
aggregator
. aggregator
must respond to
step
and finalize
. step
will be
called with row information and finalize
must return the
return value for the aggregator function.
static VALUE define_aggregator(VALUE self, VALUE name, VALUE aggregator) { sqlite3RubyPtr ctx; int arity, status; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); arity = sqlite3_obj_method_arity(aggregator, rb_intern("step")); status = sqlite3_create_function( ctx->db, StringValuePtr(name), arity, SQLITE_UTF8, (void *)aggregator, NULL, rb_sqlite3_step, rb_sqlite3_final ); rb_iv_set(self, "@agregator", aggregator); CHECK(ctx->db, status); return self; }
Define a function named name
with args
. The
arity of the block will be used as the arity for the function defined.
static VALUE define_function(VALUE self, VALUE name) { sqlite3RubyPtr ctx; VALUE block; int status; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); block = rb_block_proc(); status = sqlite3_create_function( ctx->db, StringValuePtr(name), rb_proc_arity(block), SQLITE_UTF8, (void *)block, rb_sqlite3_func, NULL, NULL ); CHECK(ctx->db, status); rb_hash_aset(rb_iv_get(self, "@functions"), name, block); return self; }
Enable or disable extension loading.
static VALUE enable_load_extension(VALUE self, VALUE onoff) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); CHECK(ctx->db, sqlite3_enable_load_extension(ctx->db, (int)NUM2INT(onoff))); return self; }
Fetch the encoding set on this database
static VALUE db_encoding(VALUE self) { sqlite3RubyPtr ctx; VALUE enc; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); enc = rb_iv_get(self, "@encoding"); if(NIL_P(enc)) { sqlite3_exec(ctx->db, "PRAGMA encoding", enc_cb, (void *)self, NULL); } return rb_iv_get(self, "@encoding"); }
Return an integer representing the last error to have occurred with this database.
static VALUE errcode_(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); return INT2NUM((long)sqlite3_errcode(ctx->db)); }
Return a string describing the last error to have occurred with this database.
static VALUE errmsg(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); return rb_str_new2(sqlite3_errmsg(ctx->db)); }
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.
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, query, and execute_batch for additional ways of executing statements.
# File lib/sqlite3/database.rb, line 115 def execute sql, bind_vars = [], *args, &block # FIXME: This is a terrible hack and should be removed but is required # for older versions of rails hack = Object.const_defined?(:ActiveRecord) && sql =~ %r^PRAGMA index_list/ if bind_vars.nil? || !args.empty? if args.empty? bind_vars = [] else bind_vars = [bind_vars] + args end warn("#{caller[0]} is calling SQLite3::Database#execute with nil or multiple bind params without using an array. Please switch to passing bind parameters as an array. Support for bind parameters as *args will be removed in 2.0.0. ") if $VERBOSE end prepare( sql ) do |stmt| stmt.bind_params(bind_vars) columns = stmt.columns stmt = ResultSet.new(self, stmt).to_a if type_translation if block_given? stmt.each do |row| if @results_as_hash yield type_translation ? row : ordered_map_for(columns, row) else yield row end end else if @results_as_hash stmt.map { |row| h = type_translation ? row : ordered_map_for(columns, row) # FIXME UGH TERRIBLE HACK! h['unique'] = h['unique'].to_s if hack h } else stmt.to_a end end end 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, query, and execute_batch for additional ways of executing statements.
# File lib/sqlite3/database.rb, line 174 def execute2( sql, *bind_vars ) prepare( sql ) do |stmt| result = stmt.execute( *bind_vars ) if block_given? yield stmt.columns result.each { |row| yield row } else return result.inject( [ stmt.columns ] ) { |arr,row| arr << row; arr } end end 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.
# File lib/sqlite3/database.rb, line 195 def execute_batch( sql, bind_vars = [], *args ) # FIXME: remove this stuff later unless [Array, Hash].include?(bind_vars.class) bind_vars = [bind_vars] warn("#{caller[0]} is calling SQLite3::Database#execute_batch with bind parameters that are not a list of a hash. Please switch to passing bind parameters as an array or hash. Support for this behavior will be removed in version 2.0.0. ") if $VERBOSE end # FIXME: remove this stuff later if bind_vars.nil? || !args.empty? if args.empty? bind_vars = [] else bind_vars = [nil] + args end warn("#{caller[0]} is calling SQLite3::Database#execute_batch with nil or multiple bind params without using an array. Please switch to passing bind parameters as an array. Support for this behavior will be removed in version 2.0.0. ") if $VERBOSE end sql = sql.strip until sql.empty? do prepare( sql ) do |stmt| # FIXME: this should probably use sqlite3's api for batch execution # This implementation requires stepping over the results. if bind_vars.length == stmt.bind_parameter_count stmt.bind_params(bind_vars) end stmt.step sql = stmt.remainder.strip end end nil end
# File lib/sqlite3/database.rb, line 393 def finalize super(@ctx) 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.
# File lib/sqlite3/database.rb, line 279 def get_first_row( sql, *bind_vars ) execute( sql, *bind_vars ).first 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.
# File lib/sqlite3/database.rb, line 288 def get_first_value( sql, *bind_vars ) execute( sql, *bind_vars ) { |row| return row[0] } nil end
Interrupts the currently executing operation, causing it to abort.
static VALUE interrupt(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); sqlite3_interrupt(ctx->db); return self; }
Obtains the unique row ID of the last row to be inserted by this Database instance.
static VALUE last_insert_row_id(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); return LL2NUM(sqlite3_last_insert_rowid(ctx->db)); }
Loads an SQLite extension library from the named file. Extension loading must be enabled using db.enable_load_extension(1) prior to calling this API.
static VALUE load_extension(VALUE self, VALUE file) { sqlite3RubyPtr ctx; int status; char *errMsg; VALUE errexp; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); status = sqlite3_load_extension(ctx->db, RSTRING_PTR(file), 0, &errMsg); if (status != SQLITE_OK) { errexp = rb_exc_new2(rb_eRuntimeError, errMsg); sqlite3_free(errMsg); rb_exc_raise(errexp); } return self; }
Returns a Statement object representing the given SQL. This does not execute the statement; it merely prepares the statement for execution.
The Statement can then be executed using SQLite3::Statement#execute.
# File lib/sqlite3/database.rb, line 90 def prepare sql stmt = SQLite3::Statement.new( self, sql ) return stmt unless block_given? begin yield stmt ensure stmt.close end end
This is a convenience method for creating a statement, binding paramters to it, and calling execute:
result = db.query( "select * from foo where a=?", 5 ) # is the same as result = db.prepare( "select * from foo where a=?" ).execute( 5 )
You must be sure to call close
on the ResultSet instance that is returned, or you could
have problems with locks on the table. If called with a block,
close
will be invoked implicitly when the block terminates.
# File lib/sqlite3/database.rb, line 247 def query( sql, bind_vars = [], *args ) if bind_vars.nil? || !args.empty? if args.empty? bind_vars = [] else bind_vars = [nil] + args end warn("#{caller[0]} is calling SQLite3::Database#query with nil or multiple bind params without using an array. Please switch to passing bind parameters as an array. Support for this will be removed in version 2.0.0. ") if $VERBOSE end result = prepare( sql ).execute( bind_vars ) if block_given? begin yield result ensure result.close end else return result end end
Returns true
if the database has been open in readonly mode A
helper to check before performing any operation
# File lib/sqlite3/database.rb, line 521 def readonly? @readonly 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
.
# File lib/sqlite3/database.rb, line 514 def rollback execute "rollback transaction" true end
# File lib/sqlite3/database.rb, line 389 def step( *args ) super(@ctx, *args) end
Returns the total number of changes made to this database instance since it was opened.
static VALUE total_changes(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); return INT2NUM((long)sqlite3_total_changes(ctx->db)); }
Installs (or removes) a block that will be invoked for every SQL statement
executed. The block receives one parameter: the SQL statement executed. If
the block is nil
, any existing tracer will be uninstalled.
static VALUE trace(int argc, VALUE *argv, VALUE self) { sqlite3RubyPtr ctx; VALUE block; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); rb_scan_args(argc, argv, "01", &block); if(NIL_P(block) && rb_block_given_p()) block = rb_block_proc(); rb_iv_set(self, "@tracefunc", block); sqlite3_trace(ctx->db, NIL_P(block) ? NULL : tracefunc, (void *)self); return self; }
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.
The mode
parameter may be either :deferred
(the
default), :immediate
, or :exclusive
.
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.
# File lib/sqlite3/database.rb, line 483 def transaction( mode = :deferred ) execute "begin #{mode.to_s} transaction" if block_given? abort = false begin yield self rescue ::Object abort = true raise ensure abort and rollback or commit end end true end
Returns true
if there is a transaction active, and
false
otherwise.
static VALUE transaction_active_p(VALUE self) { sqlite3RubyPtr ctx; Data_Get_Struct(self, sqlite3Ruby, ctx); REQUIRE_OPEN_DB(ctx); return sqlite3_get_autocommit(ctx->db) ? Qfalse : Qtrue; }
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.)
# File lib/sqlite3/database.rb, line 73 def translator @translator ||= Translator.new end