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
- NUMERIC
- ONLY_OFFSET
- OR
- PAREN_CLOSE
- SELECT_VALUES
Public Instance Methods
# File lib/sequel/adapters/shared/sqlite.rb, line 576 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
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 592 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 :^ 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.at(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 << PAREN_CLOSE if invert sql << "))" end 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
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 637 def constant_sql_append(sql, constant) if c = CONSTANT_MAP[constant] sql << c else super end end
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 648 def delete @opts[:where] ? super : where(1=>1).delete end
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 655 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 requires GROUP BY on SQLite
# File lib/sequel/adapters/shared/sqlite.rb, line 665 def having(*cond) raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group] super end
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 699 def insert_conflict(resolution = :ignore) clone(:insert_conflict => resolution) end
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 708 def insert_ignore insert_conflict(:ignore) end
SQLite uses the nonstandard ` (backtick) for quoting identifiers.
# File lib/sequel/adapters/shared/sqlite.rb, line 671 def quoted_identifier_append(sql, c) sql << BACKTICK << c.to_s.gsub(BACKTICK_RE, DOUBLE_BACKTICK) << BACKTICK end
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 679 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
SQLite 3.8.3+ supports common table expressions.
# File lib/sequel/adapters/shared/sqlite.rb, line 713 def supports_cte?(type=:select) db.sqlite_version >= 30803 end
SQLite does not support table aliases with column aliases
# File lib/sequel/adapters/shared/sqlite.rb, line 718 def supports_derived_column_lists? false end
SQLite does not support INTERSECT ALL or EXCEPT ALL
# File lib/sequel/adapters/shared/sqlite.rb, line 723 def supports_intersect_except_all? false end
SQLite does not support IS TRUE
# File lib/sequel/adapters/shared/sqlite.rb, line 728 def supports_is_true? false end
SQLite does not support multiple columns for the IN/NOT IN operators
# File lib/sequel/adapters/shared/sqlite.rb, line 733 def supports_multiple_column_in? false end
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 740 def supports_timestamp_timezones? db.use_timestamp_timezones? end
SQLite cannot use WHERE 't'.
# File lib/sequel/adapters/shared/sqlite.rb, line 745 def supports_where_true? false end
Private Instance Methods
SQLite treats a DELETE with no WHERE clause as a TRUNCATE
# File lib/sequel/adapters/shared/sqlite.rb, line 838 def _truncate_sql(table) "DELETE FROM #{table}" end
If col is a qualified column, alias it to the same as the column name
# File lib/sequel/adapters/shared/sqlite.rb, line 760 def alias_qualified_column(col) case col when Symbol t, c, a = split_symbol(col) if t && !a alias_qualified_column(SQL::QualifiedIdentifier.new(t, c)) else col end when SQL::QualifiedIdentifier SQL::AliasedExpression.new(col, col.column) else col end end
SQLite uses string literals instead of identifiers in AS clauses.
# File lib/sequel/adapters/shared/sqlite.rb, line 752 def as_sql_append(sql, aliaz, column_aliases=nil) raise Error, "sqlite does not support derived column lists" if column_aliases aliaz = aliaz.value if aliaz.is_a?(SQL::Identifier) sql << AS literal_append(sql, aliaz.to_s) end
SQLite supports a maximum of 500 rows in a VALUES clause.
# File lib/sequel/adapters/shared/sqlite.rb, line 777 def default_import_slice 500 end
SQL fragment specifying a list of identifiers
# File lib/sequel/adapters/shared/sqlite.rb, line 782 def identifier_list(columns) columns.map{|i| quote_identifier(i)}.join(COMMA) end
SQLite uses a preceding X for hex escaping strings
# File lib/sequel/adapters/shared/sqlite.rb, line 794 def literal_blob_append(sql, v) sql << BLOB_START << v.unpack(HSTAR).first << APOS end
Respect the database integer_booleans setting, using 0 or 'f'.
# File lib/sequel/adapters/shared/sqlite.rb, line 799 def literal_false @db.integer_booleans ? '0' : "'f'" end
Respect the database integer_booleans setting, using 1 or 't'.
# File lib/sequel/adapters/shared/sqlite.rb, line 804 def literal_true @db.integer_booleans ? '1' : "'t'" end
SQLite only supporting multiple rows in the VALUES clause starting in 3.7.11. On older versions, fallback to using a UNION.
# File lib/sequel/adapters/shared/sqlite.rb, line 810 def multi_insert_sql_strategy db.sqlite_version >= 30711 ? :values : :union end
SQLite does not support FOR UPDATE, but silently ignore it instead of raising an error for compatibility with other databases.
# File lib/sequel/adapters/shared/sqlite.rb, line 817 def select_lock_sql(sql) super unless @opts[:lock] == :update end
# File lib/sequel/adapters/shared/sqlite.rb, line 821 def select_only_offset_sql(sql) sql << ONLY_OFFSET literal_append(sql, @opts[:offset]) end
Support VALUES clause instead of the SELECT clause to return rows.
# File lib/sequel/adapters/shared/sqlite.rb, line 827 def select_values_sql(sql) sql << SELECT_VALUES expression_list_append(sql, opts[:values]) end
SQLite supports quoted function names.
# File lib/sequel/adapters/shared/sqlite.rb, line 833 def supports_quoted_function_names? true end