Class Sequel::Postgres::Dataset
In: lib/sequel/adapters/postgres.rb
Parent: Sequel::Dataset

Dataset class for PostgreSQL datasets that use the pg, postgres, or postgres-pr driver.

Methods

Included Modules

Sequel::Postgres::DatasetMethods

Classes and Modules

Module Sequel::Postgres::Dataset::ArgumentMapper
Module Sequel::Postgres::Dataset::BindArgumentMethods
Module Sequel::Postgres::Dataset::PreparedStatementMethods

Constants

PREPARED_ARG_PLACEHOLDER = LiteralString.new('$').freeze

Public Instance methods

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

[Source]

     # File lib/sequel/adapters/postgres.rb, line 416
416:         def call(type, bind_vars={}, *values, &block)
417:           ps = to_prepared_statement(type, values)
418:           ps.extend(BindArgumentMethods)
419:           ps.call(bind_vars, &block)
420:         end

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

[Source]

     # File lib/sequel/adapters/postgres.rb, line 308
308:       def fetch_rows(sql, &block)
309:         return cursor_fetch_rows(sql, &block) if @opts[:cursor]
310:         execute(sql){|res| yield_hash_rows(res, fetch_rows_set_cols(res), &block)}
311:       end

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

[Source]

     # File lib/sequel/adapters/postgres.rb, line 424
424:         def prepare(type, name=nil, *values)
425:           ps = to_prepared_statement(type, values)
426:           ps.extend(PreparedStatementMethods)
427:           if name
428:             ps.prepared_statement_name = name
429:             db.prepared_statements[name] = ps
430:           end
431:           ps
432:         end

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

[Source]

     # File lib/sequel/adapters/postgres.rb, line 438
438:         def prepared_arg_placeholder
439:           PREPARED_ARG_PLACEHOLDER
440:         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.

Usage:

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

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

[Source]

     # File lib/sequel/adapters/postgres.rb, line 328
328:       def use_cursor(opts={})
329:         clone(:cursor=>{:rows_per_fetch=>1000}.merge(opts))
330:       end

[Validate]