Module: Sequel::SQLite::DatasetMethods

Included in:
Amalgalite::Dataset, Dataset, Sequel::Swift::SQLite::Dataset
Defined in:
lib/sequel/adapters/shared/sqlite.rb

Overview

Instance methods for datasets that connect to an SQLite database

Constant Summary collapse

SELECT_CLAUSE_METHODS = 
Dataset.clause_methods(:select, %w'select distinct columns from join where group having compounds order limit')
CONSTANT_MAP = 
{:CURRENT_DATE=>"date(CURRENT_TIMESTAMP, 'localtime')".freeze, :CURRENT_TIMESTAMP=>"datetime(CURRENT_TIMESTAMP, 'localtime')".freeze, :CURRENT_TIME=>"time(CURRENT_TIMESTAMP, 'localtime')".freeze}
EMULATED_FUNCTION_MAP = 
{:char_length=>'length'.freeze}
EXTRACT_MAP = 
{:year=>"'%Y'", :month=>"'%m'", :day=>"'%d'", :hour=>"'%H'", :minute=>"'%M'", :second=>"'%f'"}
NOT_SPACE = 
Dataset::NOT_SPACE
COMMA = 
Dataset::COMMA
PAREN_CLOSE = 
Dataset::PAREN_CLOSE
AS = 
Dataset::AS
APOS = 
Dataset::APOS
EXTRACT_OPEN = 
"CAST(strftime(".freeze
EXTRACT_CLOSE = 
') AS '.freeze
NUMERIC = 
'NUMERIC'.freeze
INTEGER = 
'INTEGER'.freeze
BACKTICK = 
'`'.freeze
BACKTICK_RE = 
/`/.freeze
DOUBLE_BACKTICK = 
'``'.freeze
BLOB_START = 
"X'".freeze
HSTAR = 
"H*".freeze
DATE_OPEN = 
"date(".freeze
DATETIME_OPEN = 
"datetime(".freeze

Instance Method Summary collapse

Instance Method Details

#cast_sql_append(sql, expr, type) ⇒ Object 



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 497

def cast_sql_append(sql, expr, type)
  if type == Time or type == DateTime
    sql << DATETIME_OPEN
    literal_append(sql, expr)
    sql << PAREN_CLOSE
  elsif type == Date
    sql << DATE_OPEN
    literal_append(sql, expr)
    sql << PAREN_CLOSE
  else
    super
  end
end

#complex_expression_sql_append(sql, op, args) ⇒ Object

SQLite doesn’t support a NOT LIKE b, you need to use NOT (a LIKE b). It doesn’t support xor or the extract function natively, so those have to be emulated.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 513

def complex_expression_sql_append(sql, op, args)
  case op
  when :"NOT LIKE", :"NOT ILIKE"
    sql << NOT_SPACE
    complex_expression_sql_append(sql, (op == :"NOT ILIKE" ? :ILIKE : :LIKE), args)
  when :^
    sql << complex_expression_arg_pairs(args) do |a, b|
      a = literal(a)
      b = literal(b)
      "((~(#{a} & #{b})) & (#{a} | #{b}))"
    end
  when :extract
    part = args.at(0)
    raise(Sequel::Error, "unsupported extract argument: #{part.inspect}") unless format = EXTRACT_MAP[part]
    sql << EXTRACT_OPEN << format << COMMA
    literal_append(sql, args.at(1))
    sql << EXTRACT_CLOSE << (part == :second ? NUMERIC : INTEGER) << PAREN_CLOSE
  else
    super
  end
end

#constant_sql_append(sql, constant) ⇒ Object

SQLite has CURRENT_TIMESTAMP and related constants in UTC instead of in localtime, so convert those constants to local time.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 537

def constant_sql_append(sql, constant)
  if c = CONSTANT_MAP[constant]
    sql << c
  else
    super
  end
end

#delete ⇒ Object

SQLite performs a TRUNCATE style DELETE if no filter is specified. Since we want to always return the count of records, add a condition that is always true and then delete.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 548

def delete
  @opts[:where] ? super : where(1=>1).delete
end

#explain(opts = nil) ⇒ Object

Return an array of strings specifying a query explanation for a SELECT of the current dataset. Currently, the options are ignore, but it accepts options to be compatible with other adapters.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 555

def explain(opts=nil)
  # Load the PrettyTable class, needed for explain output
  Sequel.extension(:_pretty_table) unless defined?(Sequel::PrettyTable)

  ds = db.send(:metadata_dataset).clone(:sql=>"EXPLAIN #{select_sql}")
  rows = ds.all
  Sequel::PrettyTable.string(rows, ds.columns)
end

#having(*cond) ⇒ Object

HAVING requires GROUP BY on SQLite

Raises:



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 565

def having(*cond)
  raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
  super
end

#quoted_identifier_append(sql, c) ⇒ Object

SQLite uses the nonstandard ‘ (backtick) for quoting identifiers.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 571

def quoted_identifier_append(sql, c)
  sql << BACKTICK << c.to_s.gsub(BACKTICK_RE, DOUBLE_BACKTICK) << BACKTICK
end

#select(*cols) ⇒ Object

When a qualified column is selected on SQLite and the qualifier is a subselect, the column name used is the full qualified name (including the qualifier) instead of just the column name. To get correct column names, you must use an alias.



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# File 'lib/sequel/adapters/shared/sqlite.rb', line 579

def select(*cols)
  if ((f = @opts[:from]) && f.any?{|t| t.is_a?(Dataset) || (t.is_a?(SQL::AliasedExpression) && t.expression.is_a?(Dataset))}) || ((j = @opts[:join]) && j.any?{|t| t.table.is_a?(Dataset)})
    super(*cols.map{|c| alias_qualified_column(c)})
  else
    super
  end
end

#supports_intersect_except_all? ⇒ Boolean

SQLite does not support INTERSECT ALL or EXCEPT ALL

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 588

def supports_intersect_except_all?
  false
end

#supports_is_true? ⇒ Boolean

SQLite does not support IS TRUE

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 593

def supports_is_true?
  false
end

#supports_multiple_column_in? ⇒ Boolean

SQLite does not support multiple columns for the IN/NOT IN operators

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 598

def supports_multiple_column_in?
  false
end

#supports_timestamp_timezones? ⇒ Boolean

SQLite supports timezones in literal timestamps, since it stores them as text. But using timezones in timestamps breaks SQLite datetime functions, so we allow the user to override the default per database.

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 605

def supports_timestamp_timezones?
  db.use_timestamp_timezones?
end

#supports_where_true? ⇒ Boolean

SQLite cannot use WHERE ‘t’.

Returns:

  • (Boolean) 


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# File 'lib/sequel/adapters/shared/sqlite.rb', line 610

def supports_where_true?
  false
end