Class: Google::Cloud::Spanner::Results

Inherits:

Object

• Object
• Google::Cloud::Spanner::Results

Defined in:

lib/google/cloud/spanner/results.rb

Overview

Results

Represents the result set from an operation returning data.

See Client#execute_query and Client#read.

Examples:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

db = spanner.client "my-instance", "my-database"

results = db.execute_query "SELECT * FROM users"

results.fields.pairs.each do |name, type|
  puts "Column #{name} is type #{type}"
end

Instance Method Summary

• #fields ⇒ Fields

  Returns the configuration object (Fields) of the names and types of the rows in the returned data.

• #rows {|row| ... } ⇒ Object

  The values returned from the request.

• #timestamp ⇒ Time

  The read timestamp chosen for single-use snapshots (read-only transactions).

Instance Method Details

#fields ⇒ Fields

Returns the configuration object (Fields) of the names and types of the rows in the returned data.

Examples:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

db = spanner.client "my-instance", "my-database"

results = db.execute_query "SELECT * FROM users"

results.fields.pairs.each do |name, type|
  puts "Column #{name} is type #{type}"
end

Returns:

• (Fields) —

  The fields of the returned data.

# File 'lib/google/cloud/spanner/results.rb', line 77

def fields
  @fields ||= Fields.from_grpc @metadata.row_type.fields
end

#rows {|row| ... } ⇒ Object

The values returned from the request.

Examples:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

db = spanner.client "my-instance", "my-database"

results = db.execute_query "SELECT * FROM users"

results.rows.each do |row|
  puts "User #{row[:id]} is #{row[:name]}"
end

Yields:

• (row) —

  An enumerator for the rows.

Yield Parameters:

• row (Data) —

  object that contains the data values.

# File 'lib/google/cloud/spanner/results.rb', line 109

def rows
  return nil if @closed

  unless block_given?
    return enum_for(:rows)
  end

  fields = @metadata.row_type.fields
  values = []
  buffered_responses = []
  buffer_upper_bound = 10
  chunked_value = nil
  resume_token = nil
  should_resume_request = false
  should_retry_request = false

  # Cannot call Enumerator#each because it won't return the first
  # value that was already identified when calling Enumerator#peek.
  # Iterate only using Enumerator#next and break on StopIteration.
  loop do
    begin
      if should_resume_request
        @enum = resume_request(resume_token)
        buffered_responses = []
        should_resume_request = false
      elsif should_retry_request
        @enum = retry_request()
        buffered_responses = []
        should_retry_request = false
      end

      grpc = @enum.next
      # metadata should be set before the first iteration...
      @metadata ||= grpc.metadata
      @stats ||= grpc.stats

      buffered_responses << grpc

      if (grpc.resume_token && grpc.resume_token != "") ||
        buffered_responses.size >= buffer_upper_bound
        # This can set the resume_token to nil
        resume_token = grpc.resume_token

        if fields.count > 0
          buffered_responses.each do |resp|
            if chunked_value
              resp.values.unshift merge(chunked_value, resp.values.shift)
              chunked_value = nil
            end
            to_iterate = values + Array(resp.values)
            chunked_value = to_iterate.pop if resp.chunked_value
            values = to_iterate.pop(to_iterate.count % fields.count)
            to_iterate.each_slice(fields.count) do |slice|
              yield Data.from_grpc(slice, fields)
            end
          end
        end

        # Flush the buffered responses now that they are all handled
        buffered_responses = []
      end
    # TODO: once the generated client throws only Google Cloud errors, remove
    # the GRPC errors from the rescue block
    rescue GRPC::Aborted,
      GRPC::Cancelled,
      GRPC::DeadlineExceeded,
      GRPC::Internal,
      GRPC::ResourceExhausted,
      GRPC::Unauthenticated,
      GRPC::Unavailable,
      GRPC::Core::CallError,
      Google::Cloud::AbortedError,
      Google::Cloud::CanceledError,
      Google::Cloud::DeadlineExceededError,
      Google::Cloud::InternalError,
      Google::Cloud::ResourceExhaustedError,
      Google::Cloud::UnauthenticatedError,
      Google::Cloud::UnavailableError => err

      if resumable?(resume_token)
        should_resume_request = true
      elsif @service.retryable?(err)
        should_retry_request = true
      elsif err.is_a?(Google::Cloud::Error)
        raise err
      else
        raise Google::Cloud::Error.from_error(err)
      end

    # TODO: once the generated client throws only Google Cloud errors, remove
    # this rescue block (for GRPC::BadStatus)
    rescue GRPC::BadStatus => err
      raise Google::Cloud::Error.from_error(err)
    rescue StopIteration
      break
    end
  end

  # clear out any remaining values left over
  if fields.count > 0
    buffered_responses.each do |resp|
      if chunked_value
        resp.values.unshift merge(chunked_value, resp.values.shift)
        chunked_value = nil
      end
      to_iterate = values + Array(resp.values)
      chunked_value = to_iterate.pop if resp.chunked_value
      values = to_iterate.pop(to_iterate.count % fields.count)
      to_iterate.each_slice(fields.count) do |slice|
        yield Data.from_grpc(slice, fields)
      end
    end
    values.each_slice(fields.count) do |slice|
      yield Data.from_grpc(slice, fields)
    end
  end

  # If we get this far then we can release the session
  @closed = true
  nil
end

#timestamp ⇒ Time

The read timestamp chosen for single-use snapshots (read-only transactions).

Returns:

• (Time) —

  The chosen timestamp.

# File 'lib/google/cloud/spanner/results.rb', line 53

def timestamp
  return nil if @metadata.nil? || @metadata.transaction.nil?
  Convert.timestamp_to_time @metadata.transaction.read_timestamp
end