Class: Sequel::Postgres::Dataset

Inherits:
Dataset show all
Includes:
DatasetMethods
Defined in:
lib/sequel/adapters/postgres.rb

Overview

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

Defined Under Namespace

Modules: ArgumentMapper, BindArgumentMethods, PreparedStatementMethods

Constant Summary collapse

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

Constants inherited from Dataset

Dataset::AND_SEPARATOR, Dataset::ARG_BLOCK_ERROR_MSG, Dataset::ARRAY_ACCESS_ERROR_MSG, Dataset::BOOL_FALSE, Dataset::BOOL_TRUE, Dataset::COLUMN_CHANGE_OPTS, Dataset::COLUMN_REF_RE1, Dataset::COLUMN_REF_RE2, Dataset::COLUMN_REF_RE3, Dataset::COMMA_SEPARATOR, Dataset::CONDITIONED_JOIN_TYPES, Dataset::COUNT_FROM_SELF_OPTS, Dataset::COUNT_OF_ALL_AS_COUNT, Dataset::DATASET_ALIAS_BASE_NAME, Dataset::DELETE_CLAUSE_METHODS, Dataset::FROM_SELF_KEEP_OPTS, Dataset::IMPORT_ERROR_MSG, Dataset::INSERT_CLAUSE_METHODS, Dataset::IS_LITERALS, Dataset::IS_OPERATORS, Dataset::MUTATION_METHODS, Dataset::NON_SQL_OPTIONS, Dataset::NOTIMPL_MSG, Dataset::NULL, Dataset::N_ARITY_OPERATORS, Dataset::QUALIFY_KEYS, Dataset::QUESTION_MARK, Dataset::SELECT_CLAUSE_METHODS, Dataset::SQL_WITH, Dataset::STANDARD_TIMESTAMP_FORMAT, Dataset::TIMESTAMP_FORMAT, Dataset::TWO_ARITY_OPERATORS, Dataset::UNCONDITIONED_JOIN_TYPES, Dataset::UPDATE_CLAUSE_METHODS, Dataset::WILDCARD, Dataset::WITH_SUPPORTED

Instance Attribute Summary

Attributes inherited from Dataset

#db, #identifier_input_method, #identifier_output_method, #opts, #quote_identifiers, #row_proc

Instance Method Summary collapse

Methods inherited from Dataset

#<<, #[], #[]=, #add_graph_aliases, #aliased_expression_sql, #all, #and, #array_sql, #as, #avg, #bind, #boolean_constant_sql, #case_expression_sql, #cast_sql, clause_methods, #clone, #column_all_sql, #columns, #columns!, #complex_expression_sql, #constant_sql, #count, def_mutation_method, #def_mutation_method, #delete, #delete_sql, #distinct, #each, #each_page, #empty?, #except, #exclude, #exists, #filter, #first, #first_source_alias, #from, #from_self, #function_sql, #get, #graph, #grep, #group, #group_and_count, #having, #import, #initialize, #insert, #insert_multiple, #insert_sql, #inspect, #intersect, #interval, #invert, #join_clause_sql, #join_on_clause_sql, #join_table, #join_using_clause_sql, #last, #limit, #literal, #map, #max, #min, #multi_insert, #multi_insert_sql, #naked, #negative_boolean_constant_sql, #or, #order, #order_more, #ordered_expression_sql, #paginate, #placeholder_literal_string_sql, #print, #qualified_identifier_sql, #qualify, #qualify_to, #qualify_to_first_source, #query, #quote_identifier, #quote_identifiers?, #quote_schema_table, #quoted_identifier, #range, #requires_sql_standard_datetimes?, #reverse_order, #schema_and_table, #select, #select_all, #select_hash, #select_map, #select_more, #select_order_map, #select_sql, #server, #set, #set_defaults, #set_graph_aliases, #set_overrides, #single_record, #single_value, #sql, #subscript_sql, #sum, #supports_cte?, #supports_distinct_on?, #supports_intersect_except?, #supports_intersect_except_all?, #supports_is_true?, #supports_join_using?, #supports_modifying_joins?, #supports_multiple_column_in?, #supports_timestamp_timezones?, #supports_timestamp_usecs?, #supports_window_functions?, #to_csv, #to_hash, #truncate, #truncate_sql, #unfiltered, #ungraphed, #ungrouped, #union, #unlimited, #unordered, #update, #update_sql, #where, #window_function_sql, #window_sql, #with, #with_recursive, #with_sql

Methods included from Metaprogramming

#meta_def

Constructor Details

This class inherits a constructor from Sequel::Dataset

Instance Method Details

#call(type, bind_vars = {}, *values, &block) ⇒ Object

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



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# File 'lib/sequel/adapters/postgres.rb', line 416

def call(type, bind_vars={}, *values, &block)
  ps = to_prepared_statement(type, values)
  ps.extend(BindArgumentMethods)
  ps.call(bind_vars, &block)
end

#fetch_rows(sql, &block) ⇒ Object

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



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# File 'lib/sequel/adapters/postgres.rb', line 308

def fetch_rows(sql, &block)
  return cursor_fetch_rows(sql, &block) if @opts[:cursor]
  execute(sql){|res| yield_hash_rows(res, fetch_rows_set_cols(res), &block)}
end

#prepare(type, name = nil, *values) ⇒ Object

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



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# File 'lib/sequel/adapters/postgres.rb', line 424

def prepare(type, name=nil, *values)
  ps = to_prepared_statement(type, values)
  ps.extend(PreparedStatementMethods)
  if name
    ps.prepared_statement_name = name
    db.prepared_statements[name] = ps
  end
  ps
end

#use_cursor(opts = {}) ⇒ Object

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.



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# File 'lib/sequel/adapters/postgres.rb', line 328

def use_cursor(opts={})
  clone(:cursor=>{:rows_per_fetch=>1000}.merge(opts))
end