actualize_join_plan: Execute an ordered sequence of left joins.

In WinVector/rquery: Relational Query Generator for Data Manipulation at Scale

Execute an ordered sequence of left joins.

Description

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

Usage

actualize_join_plan(
  columnJoinPlan,
  ...,
  jointype = "LEFT",
  add_ind_cols = FALSE,
  checkColClasses = FALSE
)

Arguments

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.
jointype	character, type of join to perform ("LEFT", "INNER", "RIGHT", ...).
add_ind_cols	logical, if TRUE add indicators showing which tables supplied rows.
checkColClasses	logical if true check for exact class name matches

Value

join optree

See Also

describe_tables, build_join_plan, inspect_join_plan, graph_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,
                    "meas1",
                    data.frame(id= c(1,2),
                               weight= c(200, 120),
                               height= c(60, 14)))
  DBI::dbWriteTable(my_db,
                    "meas2",
                    data.frame(pid= c(2,3),
                               weight= c(105, 110),
                               width= 1))
  # get the initial description of table defs
  tDesc <- describe_tables(my_db, qc(meas1, meas2))
  # declare keys (and give them consitent names)
  tDesc$keys[[1]] <- list(PatientID= 'id')
  tDesc$keys[[2]] <- list(PatientID= 'pid')
  # build the column join plan
  columnJoinPlan <- build_join_plan(tDesc)
  # decide we don't want the width column
  columnJoinPlan$want[columnJoinPlan$resultColumn=='width'] <- FALSE
  # double check our plan
  if(!is.null(inspect_join_plan(tDesc, columnJoinPlan,
                                checkColClasses= TRUE))) {
    stop("bad join plan")
  }
  # actualize as left join op_tree
  optree <- actualize_join_plan(columnJoinPlan,
                                checkColClasses= TRUE)
  cat(format(optree))
  print(execute(my_db, optree))
  # if(requireNamespace("DiagrammeR", quietly = TRUE)) {
  #   DiagrammeR::grViz(op_diagram(optree))
  # }
  DBI::dbDisconnect(my_db)
}

WinVector/rquery documentation built on Aug. 24, 2023, 11:12 a.m.