# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 151
def begin_db_transaction
  execute "BEGIN"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 155
def begin_isolated_db_transaction(isolation)
  begin_db_transaction
  execute "SET TRANSACTION ISOLATION LEVEL #{transaction_isolation_levels.fetch(isolation)}"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 161
def commit_db_transaction
  execute "COMMIT"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 115
def exec_delete(sql, name = 'SQL', binds = [])
  execute_and_clear(sql, name, binds) {|result| result.cmd_tuples }
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 136
def exec_insert(sql, name, binds, pk = nil, sequence_name = nil)
  val = exec_query(sql, name, binds)
  if !use_insert_returning? && pk
    unless sequence_name
      table_ref = extract_table_ref_from_insert_sql(sql)
      sequence_name = default_sequence_name(table_ref, pk)
      return val unless sequence_name
    end
    last_insert_id_result(sequence_name)
  else
    val
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 102
def exec_query(sql, name = 'SQL', binds = [], prepare: false)
  execute_and_clear(sql, name, binds, prepare: prepare) do |result|
    types = {}
    fields = result.fields
    fields.each_with_index do |fname, i|
      ftype = result.ftype i
      fmod  = result.fmod i
      types[fname] = get_oid_type(ftype, fmod, fname)
    end
    ActiveRecord::Result.new(fields, result.values, types)
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 166
def exec_rollback_db_transaction
  execute "ROLLBACK"
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 96
def execute(sql, name = nil)
  log(sql, name) do
    @connection.async_exec(sql)
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 5
def explain(arel, binds = [])
  sql = "EXPLAIN #{to_sql(arel, binds)}"
  PostgreSQL::ExplainPrettyPrinter.new.pp(exec_query(sql, 'EXPLAIN', binds))
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 32
def select_rows(sql, name = nil, binds = [])
  execute_and_clear(sql, name, binds) do |result|
    result.values
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 10
def select_value(arel, name = nil, binds = [])
  arel, binds = binds_from_relation arel, binds
  sql = to_sql(arel, binds)
  execute_and_clear(sql, name, binds) do |result|
    result.getvalue(0, 0) if result.ntuples > 0 && result.nfields > 0
  end
end

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 18
def select_values(arel, name = nil, binds = [])
  arel, binds = binds_from_relation arel, binds
  sql = to_sql(arel, binds)
  execute_and_clear(sql, name, binds) do |result|
    if result.nfields > 0
      result.column_values(0)
    else
      []
    end
  end
end