topo_sort_tables: Topologically sort join plan so values are available before...

In rquery: Relational Query Generator for Data Manipulation at Scale

Topologically sort join plan so values are available before uses.

Description

Depends on igraph package. Please see vignette('DependencySorting', package = 'rquery') and vignette('joinController', package= 'rquery') for more details.

Usage

topo_sort_tables(columnJoinPlan, leftTableName, ...)

Arguments

columnJoinPlan	join plan
leftTableName	which table is left
...	force later arguments to bind by name

Value

list with dependencyGraph and sorted columnJoinPlan

Examples

if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE) &&
    requireNamespace('igraph', quietly = TRUE)) {
  # note: employeeanddate is likely built as a cross-product
  #       join of an employee table and set of dates of interest
  #       before getting to the join controller step.  We call
  #       such a table "row control" or "experimental design."
  my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
  RSQLite::initExtension(my_db)
  tDesc <- example_employee_date(my_db)
  columnJoinPlan <- build_join_plan(tDesc, check= FALSE)
  # unify keys
  columnJoinPlan$resultColumn[columnJoinPlan$resultColumn=='id'] <- 'eid'
  # look at plan defects
  print(paste('problems:',
              inspect_join_plan(tDesc, columnJoinPlan)))
  # fix plan
  sorted <- topo_sort_tables(columnJoinPlan, 'employeeanddate')
  print(paste('problems:',
              inspect_join_plan(tDesc, sorted$columnJoinPlan)))
  print(plot(sorted$dependencyGraph))
  DBI::dbDisconnect(my_db)
  my_db <- NULL
}

rquery documentation built on Aug. 20, 2023, 9:06 a.m.