Class: RdbmsSampler::Sample

Inherits:
Object
  • Object
show all
Defined in:
lib/rdbms_sampler/sample.rb

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Sample

Returns a new instance of Sample.



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# File 'lib/rdbms_sampler/sample.rb', line 8

def initialize(options ={})
  @connection = options[:conn]
  @rows_per_table = options[:rows_per_table] || 1000
  @table_samples = {}
  @schemas = options[:schemas]
  @computed = false
  @connection.execute 'SET SESSION TRANSACTION READ ONLY, ISOLATION LEVEL REPEATABLE READ'
  @connection.execute 'START TRANSACTION'
end

Instance Method Details

#compute! ⇒ Object 



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# File 'lib/rdbms_sampler/sample.rb', line 18

def compute!
  quoted_schema_names = @schemas.collect do |name|
    @connection.quote_table_name(name)
  end
  warn "Discovering tables in databases: #{quoted_schema_names.to_sentence}..."
  tables_without_views.each do |schema_name, table_name|
    table_sample = TableSample.new(@connection, schema_name, table_name, @rows_per_table)
    @table_samples[table_sample.identifier] = table_sample
  end
  return warn 'No tables found!' unless @table_samples.count > 0
  warn "Sampling #{@table_samples.count} tables..."
  @table_samples.values.map &:sample!
  warn 'Ensuring referential integrity...'
  begin
    new_dependencies = 0
    @table_samples.values.each do |table_sample|
      newly_added = table_sample.ensure_referential_integrity(self)
      if newly_added > 0
        new_dependencies += newly_added
        warn "  Expanded sample with #{newly_added} new rows referenced from table #{table_sample.quoted_name}"
      end
    end
    warn " Discovered #{new_dependencies} new dependencies" if new_dependencies > 0
  end while new_dependencies > 0
  warn 'Referential integrity obtained'

  warn 'Final sample contains:'
  @table_samples.values.each do |table_sample|
    warn "  #{table_sample.size} row(s) from `#{table_sample.identifier}`"
  end
  @computed = true
end

#table_sample_for_dependency(dependency) ⇒ TableSample

Parameters:

Returns:



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# File 'lib/rdbms_sampler/sample.rb', line 53

def table_sample_for_dependency(dependency)
  raise "Table sample for [#{dependency.identifier}] not found" unless @table_samples.include? dependency.identifier
  @table_samples[dependency.identifier]
end

#to_sql ⇒ Object 



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# File 'lib/rdbms_sampler/sample.rb', line 58

def to_sql
  compute! unless @computed
  @table_samples.values.collect(&:to_sql) * "\n"
end