class Sequel::Postgres::Dataset

Execute the given type of statement with the hash of values.

# File lib/sequel/adapters/postgres.rb, line 731
def call(type, bind_vars=OPTS, *values, &block)
  ps = to_prepared_statement(type, values)
  ps.extend(BindArgumentMethods)
  ps.call(bind_vars, &block)
end

Yield all rows returned by executing the given SQL and converting the types.

# File lib/sequel/adapters/postgres.rb, line 624
def fetch_rows(sql)
  return cursor_fetch_rows(sql){|h| yield h} if @opts[:cursor]
  execute(sql){|res| yield_hash_rows(res, fetch_rows_set_cols(res)){|h| yield h}}
end

Prepare the given type of statement with the given name, and store it in the database to be called later.

# File lib/sequel/adapters/postgres.rb, line 739
def prepare(type, name=nil, *values)
  ps = to_prepared_statement(type, values)
  ps.extend(PreparedStatementMethods)
  if name
    ps.prepared_statement_name = name
    db.set_prepared_statement(name, ps)
  end
  ps
end

PostgreSQL uses $N for placeholders instead of ?, so use a $ as the placeholder.

# File lib/sequel/adapters/postgres.rb, line 753
def prepared_arg_placeholder
  PREPARED_ARG_PLACEHOLDER
end

Uses a cursor for fetching records, instead of fetching the entire result set at once. Can be used to process large datasets without holding all rows in memory (which is what the underlying drivers do by default). Options:

• :rows_per_fetch - the number of rows per fetch (default 1000). Higher numbers result in fewer queries but greater memory use.

• :cursor_name - the name assigned to the cursor (default ‘sequel_cursor’). Nested cursors require different names.

Usage:

DB[:huge_table].use_cursor.each{|row| p row}
DB[:huge_table].use_cursor(:rows_per_fetch=>10000).each{|row| p row}
DB[:huge_table].use_cursor(:cursor_name=>'my_cursor').each{|row| p row}

This is untested with the prepared statement/bound variable support, and unlikely to work with either.

# File lib/sequel/adapters/postgres.rb, line 647
def use_cursor(opts=OPTS)
  clone(:cursor=>{:rows_per_fetch=>1000, :cursor_name => 'sequel_cursor'}.merge(opts))
end