Class: DWH::Adapters::Postgres

Inherits:
Adapter
  • Object
show all
Defined in:
lib/dwh/adapters/postgres.rb

Overview

Postgres adapter. Please ensure the pg gem is available before using this adapter. Generally, adapters should be created using DWH.create. Where a configuration is passed in as options hash or argument list.

Examples:

Basic connection with required only options

DWH.create(:postgres, {host: 'localhost', database: 'postgres',
  username: 'postgres'})

Connection with cert based SSL connection

DWH.create(:postgres, {host: 'localhost', database: 'postgres',
  username: 'postgres', ssl: true,
  extra_connection_params: { sslmode: 'require' })

valid sslmodes: disable, prefer, require, verify-ca, verify-full
For modes requiring Certs make sure you add the appropirate params
to extra_connection_params. (ie sslrootcert, sslcert etc.)

Connection sending custom application name

DWH.create(:postgres, {host: 'localhost', database: 'postgres',
  username: 'postgres', application_name: "Strata CLI" })

Direct Known Subclasses

Redshift

Constant Summary

Constants included from Settings

Settings::BASE_SETTINGS_FILE

Constants included from Functions::Dates

Functions::Dates::DATE_CLASSES, Functions::Dates::TIMESTAMPABLE_UNITS

Instance Attribute Summary

Attributes inherited from Adapter

#config, #settings

Attributes included from Settings

#adapter_settings

Instance Method Summary collapse

Methods inherited from Adapter

#adapter_name, #alter_settings, #close, config, configuration, #connect!, #connect?, #extra_connection_params, #extra_query_params, #initialize, #reset_settings, #token_expired?, #with_debug, #with_retry

Methods included from Settings

#adapter_name, #load_settings, #settings_file, #settings_file_path, #using_base_settings?

Methods included from Logger

#logger, logger

Methods included from Behaviors

#apply_advanced_filtering_on_array_projections?, #cross_universe_measure_filtering_strategy, #extend_ending_date_to_last_hour_of_day?, #final_measure_filter?, #final_pass_measure_join_type, #greedy_apply_date_filters, #intermediate_measure_filter?, #temp_table_prefix, #temp_table_type

Methods included from Functions

#cast, #cross_join, #gsk, #lower_case, #quote, #string_lit, #trim, #upper_case

Methods included from Functions::Arrays

#array_exclude_list, #array_in_list, #array_unnest_join

Methods included from Functions::Nulls

#if_null, #null_if, #null_if_zero

Methods included from Functions::ExtractDatePart

#extract_day_name, #extract_day_of_month, #extract_day_of_week, #extract_day_of_year, #extract_hour, #extract_minute, #extract_month, #extract_month_name, #extract_quarter, #extract_week_of_year, #extract_year, #extract_year_month

Methods included from Functions::Dates

#adjust_week_start_day, #adjust_week_start_day?, #current_date, #current_time, #current_timestamp, #date_data_type, #date_diff, #date_format, #date_format_sql, #date_int?, #date_lit, #date_literal, #date_time_format, #date_time_literal, #date_time_tz_format, #default_week_start_day, #timestamp_lit, #timestamp_literal, #truncate_date, #week_start_day, #week_starts_on_sunday?

Methods included from Capabilities

#supports_array_functions?, #supports_common_table_expressions?, #supports_cross_join?, #supports_full_join?, #supports_sub_queries?, #supports_table_join?, #supports_temp_tables?, #supports_window_functions?

Constructor Details

This class inherits a constructor from DWH::Adapters::Adapter

Instance Method Details

#connection ⇒ Object

Creates a connection to the target database and returns the connection object or self



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# File 'lib/dwh/adapters/postgres.rb', line 35

def connection
  return @connection if @connection

  set_default_ssl_mode_if_needed

  properties = {
    host: config[:host],
    port: config[:port],
    dbname: config[:database],
    user: config[:username],
    password: config[:password],
    application_name: config[:client_name]
  }.merge(extra_connection_params)
  properties[:options] = "#{properties[:options]} -c statement_timeout=#{config[:query_timeout] * 1000}"

  @connection = PG.connect(properties)

  # this could be comma separated list
  @connection.exec("SET search_path TO #{config[:schema]}") if schema?

  @connection
rescue StandardError => e
  raise ConfigError, e.message
end

#date_add(unit, val, exp) ⇒ Object

Need to override default add method since postgres doesn't support quarter as an interval.

Parameters:

  • unit (String) —

    Should be one of day, month, quarter etc

  • val (String, Integer) —

    The number of days to add

  • exp (String) —

    The sql expresssion to modify



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# File 'lib/dwh/adapters/postgres.rb', line 209

def date_add(unit, val, exp)
  if unit.downcase.strip == 'quarter'
    unit = 'months'
    val = val.to_i * 3
  end
  gsk(:date_add)
    .gsub(/@unit/i, unit)
    .gsub(/@val/i, val.to_s)
    .gsub(/@exp/i, exp)
end

#execute(sql, format: :array, retries: 0) ⇒ Array<Array>, ...

Execute sql on the target database.

Parameters:

  • sql (String) —

    actual sql

  • format (Symbol, String) (defaults to: :array) —

    return format type

    • array returns array of array
    • object returns array of Hashes
    • csv returns as csv
    • native returns the native result from any clients used
      • For example: Postgres using pg client will return PG::Result
      • Http clients will returns the HTTP response object
  • retries (Integer) (defaults to: 0) —

    number of retries in case of failure. Default is 0

Returns:

  • (Array<Array>, Hash, CSV, Native)

Raises:



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# File 'lib/dwh/adapters/postgres.rb', line 150

def execute(sql, format: :array, retries: 0)
  begin
    result = with_debug(sql) { with_retry(retries) { connection.exec(sql) } }
  rescue StandardError => e
    raise ExecutionError, e.message
  end

  format = format.downcase if format.is_a?(String)
  case format.to_sym
  when :array
    result.values
  when :object
    result.to_a
  when :csv
    result_to_csv(result)
  when :native
    result
  else
    raise UnsupportedCapability, "Unsupported format: #{format} for this #{name}"
  end
end

#execute_stream(sql, io, stats: nil, retries: 0) ⇒ IO

Execute sql and stream responses back. Data is writtent out in CSV format to the provided IO object.

Parameters:

  • sql (String) —

    actual sql

  • io (IO) —

    IO object to write records to

  • stats (StreamingStats) (defaults to: nil) —

    collect stats and preview data this is optional

  • retries (Integer) (defaults to: 0) —

    number of retries in case of failure

Returns:

  • (IO)

Raises:



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# File 'lib/dwh/adapters/postgres.rb', line 173

def execute_stream(sql, io, stats: nil, retries: 0)
  with_debug(sql) do
    with_retry(retries) do
      connection.exec(sql) do |result|
        io.write(CSV.generate_line(result.fields))
        result.each_row do |row|
          stats << row unless stats.nil?
          io.write(CSV.generate_line(row))
        end
      end
    end
  end

  io.rewind
  io
rescue StandardError => e
  raise ExecutionError, e.message
end

#metadata(table, **qualifiers) ⇒ DWH::Table

Get the schema structure of a given a given table_name. Pass in optional catalog and schema info.

Example: metadata("public.big_table") metadata("big_table") metadata("big_table",schema: "public")

Parameters:

  • table (String) —
    • table name
  • qualifiers (Hash) —

    a customizable set of options

Options Hash (**qualifiers):

  • :catalog (String) —

    optional catalog or equivalent name space. will be ignored if the adapter doesn't support

  • :schema (String) —

    optional schema to scope to. will be ignored if the adapter doesn't support

Returns:



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# File 'lib/dwh/adapters/postgres.rb', line 113

def metadata(table, **qualifiers)
  db_table = Table.new table, schema: qualifiers[:schema]

  schema_where = ''
  if db_table.schema?
    schema_where = "AND table_schema = '#{db_table.schema}'"
  elsif schema?
    schema_where = "AND table_schema in (#{qualified_schema_name})"
  end

  sql = <<-SQL
              SELECT column_name, data_type, character_maximum_length, numeric_precision,numeric_scale
              FROM information_schema.columns
              WHERE table_name = '#{db_table.physical_name}'
              #{schema_where}
  SQL

  cols = execute(sql, format: 'object')
  cols.each do |col|
    db_table << Column.new(
      name: col['column_name'],
      data_type: col['data_type'],
      precision: col['numeric_precision'],
      scale: col['numeric_scale'],
      max_char_length: col['character_maximum_length']
    )
  end

  db_table
end

#schema? ⇒ Boolean

True if the configuration was setup with a schema.

Returns:



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# File 'lib/dwh/adapters/postgres.rb', line 145

def schema?
  !config[:schema].nil? && !config[:schema]&.strip&.empty?
end

#stats(table, date_column: nil, **qualifiers) ⇒ DWH::Table

Returns basic stats of a given table. Will typically include row_count, date_start, and date_end.

Examples:

stats("public.big_table", date_column: "fact_date")
stats("big_table")
stats("big_table",schema: "public")

Parameters:

  • table (String) —

    table name

  • date_column (String) (defaults to: nil) —

    optional date column to use to find range

  • qualifiers (Hash) —

    a customizable set of options

Options Hash (**qualifiers):

  • :catalog (String) —

    optional catalog or equivalent name space. will be ignored if the adapter doesn't support

  • :schema (String) —

    optional schema to scope to. will be ignored if the adapter doesn't support

Returns:

Raises:



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# File 'lib/dwh/adapters/postgres.rb', line 95

def stats(table, date_column: nil, **qualifiers)
  table_name = qualifiers[:schema] ? "#{qualifiers[:schema]}.#{table}" : table
  sql = <<-SQL
              SELECT count(*) ROW_COUNT
                  #{date_column.nil? ? nil : ", min(#{date_column}) DATE_START"}
                  #{date_column.nil? ? nil : ", max(#{date_column}) DATE_END"}
              FROM "#{table_name}"
  SQL

  result = connection.exec(sql)
  TableStats.new(
    row_count: result.first['row_count'],
    date_start: result.first['date_start'],
    date_end: result.first['date_end']
  )
end

#stream(sql) {|chunk| ... } ⇒ Object

Executes the given sql and yields the streamed results to the given block.

Parameters:

  • sql (String) —

    actual sql

Yields:

  • (chunk) —

    Yields a streamed chunk as it streams in. The chunk type might vary depending on the target db and settings

Raises:



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# File 'lib/dwh/adapters/postgres.rb', line 193

def stream(sql, &block)
  with_debug(sql) do
    connection.exec(sql) do |result|
      result.each_row do |row|
        block.call(row)
      end
    end
  end
end

#table?(table_name) ⇒ Boolean

Check if table exists in remote db.

Parameters:

  • qualifiers (Hash) —

    a customizable set of options

Returns:



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# File 'lib/dwh/adapters/postgres.rb', line 90

def table?(table_name)
  tables.include?(table_name)
end

#tables(**qualifiers) ⇒ Array<String>

Get all tables available in the target db. It will use the default catalog and schema config only specified here.

Parameters:

  • qualifiers (Hash) —

    a customizable set of options

Options Hash (**qualifiers):

  • :catalog (String) —

    optional catalog or equivalent name space. will be ignored if the adapter doesn't support

  • :schema (String) —

    optional schema to scope to. will be ignored if the adapter doesn't support

Returns:

  • (Array<String>) 


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# File 'lib/dwh/adapters/postgres.rb', line 71

def tables(**qualifiers)
  sql = if schema? || qualifiers[:schema]
          <<-SQL
                  SELECT table_name#{' '}
                  FROM information_schema.tables
                  WHERE table_schema in (#{qualified_schema_name(qualifiers)})
          SQL
        else
          <<-SQL
                  SELECT table_name
                  FROM information_schema.tables
          SQL
        end

  result = connection.exec(sql)
  result.values.flatten
end

#test_connection(raise_exception: false) ⇒ Boolean

Tests the connection to the target database and returns true if successful, or raise Exception or false connection object or self

Returns:

Raises:



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# File 'lib/dwh/adapters/postgres.rb', line 61

def test_connection(raise_exception: false)
  connection
  true
rescue StandardError => e
  raise ConnectionError, e.message if raise_exception

  false
end

#valid_config? ⇒ Boolean

Returns:



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# File 'lib/dwh/adapters/postgres.rb', line 220

def valid_config?
  super
  require 'pg'
rescue LoadError
  raise ConfigError, "Required 'pg' gem missing. Please add it to your Gemfile."
end