module Sequel::SQLite::DatasetMethods

Instance methods for datasets that connect to an SQLite database

Constants

APOS
AS
BACKTICK
BACKTICK_RE
BLOB_START
COMMA
CONSTANT_MAP
DATETIME_OPEN
DATE_OPEN
DOUBLE_BACKTICK
EMULATED_FUNCTION_MAP
EXTRACT_CLOSE
EXTRACT_MAP
EXTRACT_OPEN
HSTAR
INTEGER
NOT_SPACE

EXTRACT_MAP.each_value(&:freeze) # SEQUEL5

NUMERIC
ONLY_OFFSET
OR
PAREN_CLOSE
SELECT_VALUES

Public Instance Methods

cast_sql_append(sql, expr, type) click to toggle source
# File lib/sequel/adapters/shared/sqlite.rb, line 602
def cast_sql_append(sql, expr, type)
  if type == Time or type == DateTime
    sql << "datetime("
    literal_append(sql, expr)
    sql << ')'
  elsif type == Date
    sql << "date("
    literal_append(sql, expr)
    sql << ')'
  else
    super
  end
end
complex_expression_sql_append(sql, op, args) click to toggle source

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.

# File lib/sequel/adapters/shared/sqlite.rb, line 618
def complex_expression_sql_append(sql, op, args)
  case op
  when :"NOT LIKE", :"NOT ILIKE"
    sql << 'NOT '
    complex_expression_sql_append(sql, (op == :"NOT ILIKE" ? :ILIKE : :LIKE), args)
  when :^
    complex_expression_arg_pairs_append(sql, args){|a, b| Sequel.lit(["((~(", " & ", ")) & (", " | ", "))"], a, b, a, b)}
  when :**
    unless (exp = args[1]).is_a?(Integer)
      raise(Sequel::Error, "can only emulate exponentiation on SQLite if exponent is an integer, given #{exp.inspect}")
    end
    case exp
    when 0
      sql << '1'
    else
      sql << '('
      arg = args[0]
      if exp < 0
        invert = true
        exp = exp.abs
        sql << '(1.0 / ('
      end
      (exp - 1).times do 
        literal_append(sql, arg)
        sql << " * "
      end
      literal_append(sql, arg)
      sql << ')'
      if invert
        sql << "))"
      end
    end
  when :extract
    part = args[0]
    raise(Sequel::Error, "unsupported extract argument: #{part.inspect}") unless format = EXTRACT_MAP[part]
    sql << "CAST(strftime(" << format << ', '
    literal_append(sql, args[1])
    sql << ') AS ' << (part == :second ? 'NUMERIC' : 'INTEGER') << ')'
  else
    super
  end
end
constant_sql_append(sql, constant) click to toggle source

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

# File lib/sequel/adapters/shared/sqlite.rb, line 663
def constant_sql_append(sql, constant)
  if c = CONSTANT_MAP[constant]
    sql << c
  else
    super
  end
end
delete() click to toggle source

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.

# File lib/sequel/adapters/shared/sqlite.rb, line 674
def delete
  @opts[:where] ? super : where(1=>1).delete
end
explain(opts=nil) click to toggle source

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.

# File lib/sequel/adapters/shared/sqlite.rb, line 681
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) click to toggle source

HAVING requires GROUP BY on SQLite

# File lib/sequel/adapters/shared/sqlite.rb, line 691
def having(*cond)
  raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
  super
end
insert_conflict(resolution = :ignore) click to toggle source

Handle uniqueness violations when inserting, by using a specified resolution algorithm. With no options, uses INSERT OR REPLACE. SQLite supports the following conflict resolution algoriths: ROLLBACK, ABORT, FAIL, IGNORE and REPLACE.

Examples:

DB[:table].insert_conflict.insert(:a=>1, :b=>2)
# INSERT OR IGNORE INTO TABLE (a, b) VALUES (1, 2)

DB[:table].insert_conflict(:replace).insert(:a=>1, :b=>2)
# INSERT OR REPLACE INTO TABLE (a, b) VALUES (1, 2)
# File lib/sequel/adapters/shared/sqlite.rb, line 725
def insert_conflict(resolution = :ignore)
  clone(:insert_conflict => resolution)
end
insert_ignore() click to toggle source

Ignore uniqueness/exclusion violations when inserting, using INSERT OR IGNORE. Exists mostly for compatibility to MySQL’s insert_ignore. Example:

DB[:table].insert_ignore.insert(:a=>1, :b=>2)
# INSERT OR IGNORE INTO TABLE (a, b) VALUES (1, 2)
# File lib/sequel/adapters/shared/sqlite.rb, line 734
def insert_ignore
  insert_conflict(:ignore)
end
quoted_identifier_append(sql, c) click to toggle source

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

# File lib/sequel/adapters/shared/sqlite.rb, line 697
def quoted_identifier_append(sql, c)
  sql << '`' << c.to_s.gsub('`', '``') << '`'
end
select(*cols) click to toggle source

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.

# File lib/sequel/adapters/shared/sqlite.rb, line 705
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_cte?(type=:select) click to toggle source

SQLite 3.8.3+ supports common table expressions.

# File lib/sequel/adapters/shared/sqlite.rb, line 739
def supports_cte?(type=:select)
  db.sqlite_version >= 30803
end
supports_derived_column_lists?() click to toggle source

SQLite does not support table aliases with column aliases

# File lib/sequel/adapters/shared/sqlite.rb, line 744
def supports_derived_column_lists?
  false
end
supports_intersect_except_all?() click to toggle source

SQLite does not support INTERSECT ALL or EXCEPT ALL

# File lib/sequel/adapters/shared/sqlite.rb, line 749
def supports_intersect_except_all?
  false
end
supports_is_true?() click to toggle source

SQLite does not support IS TRUE

# File lib/sequel/adapters/shared/sqlite.rb, line 754
def supports_is_true?
  false
end
supports_multiple_column_in?() click to toggle source

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

# File lib/sequel/adapters/shared/sqlite.rb, line 759
def supports_multiple_column_in?
  false
end
supports_timestamp_timezones?() click to toggle source

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.

# File lib/sequel/adapters/shared/sqlite.rb, line 766
def supports_timestamp_timezones?
  db.use_timestamp_timezones?
end
supports_where_true?() click to toggle source

SQLite cannot use WHERE ‘t’.

# File lib/sequel/adapters/shared/sqlite.rb, line 771
def supports_where_true?
  false
end