inspect_join_plan: check that a join plan is consistent with table descriptions.

In rquery: Relational Query Generator for Data Manipulation at Scale

check that a join plan is consistent with table descriptions.

Description

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

Usage

inspect_join_plan(tDesc, columnJoinPlan, ..., checkColClasses = FALSE)

Arguments

tDesc	description of tables, from describe_tables (and likely altered by user).
columnJoinPlan	columns to join, from build_join_plan (and likely altered by user). Note: no column names must intersect with names of the form table_CLEANEDTABNAME_present.
...	force later arguments to bind by name.
checkColClasses	logical if true check for exact class name matches

Value

NULL if okay, else a string

See Also

describe_tables, build_join_plan, graph_join_plan, actualize_join_plan

Examples

if (requireNamespace("DBI", quietly = TRUE) && requireNamespace("RSQLite", quietly = TRUE)) {
  my_db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
  # example data
  DBI::dbWriteTable(my_db,
                    "d1",
                    data.frame(id= 1:3,
                               weight= c(200, 140, 98),
                               height= c(60, 24, 12)))
  DBI::dbWriteTable(my_db,
                    "d2",
                    data.frame(pid= 2:3,
                               weight= c(130, 110),
                               width= 1))
  # get the initial description of table defs
  tDesc <- describe_tables(my_db, qc(d1, d2))
  # declare keys (and give them consistent names)
  tDesc$keys[[1]] <- list(PrimaryKey= 'id')
  tDesc$keys[[2]] <- list(PrimaryKey= 'pid')
  # build the join plan
  columnJoinPlan <- build_join_plan(tDesc)
  # confirm the plan
  print(inspect_join_plan(tDesc, columnJoinPlan,
                          checkColClasses= TRUE))
  # damage the plan
  columnJoinPlan$sourceColumn[columnJoinPlan$sourceColumn=='width'] <- 'wd'
  # find a problem
  print(inspect_join_plan(tDesc, columnJoinPlan,
                          checkColClasses= TRUE))
  DBI::dbDisconnect(my_db)
}

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