Rename R cross_join to join, add documentation (#4548)

* Refactor cross-join to join and add doc

* Correct test

* Generate docs

R/rdeephaven/R/table_handle_wrapper.R

@@ -388,11 +388,19 @@ TableHandle <- R6Class("TableHandle",
       return(TableHandle$new(self$.internal_rcpp_object$count_by(col, by)))
     },
 
-    #' @export
-    cross_join = function(table, on = character(), joins = character()) {
+    #' @description
+    #' Creates a new table containing rows that have matching values in both tables. Rows that do not have matching
+    #' criteria will not be included in the result. If there are multiple matches between a row from the left table
+    #' and rows from the right table, all matching combinations will be included. If no columns to match (on) are
+    #' specified, every combination of left and right table rows is included.
+    #' @param table TableHandle referencing the table to join with.
+    #' @param on String or list of strings denoting the names of the columns to join on.
+    #' @param joins String or list of strings denoting the names of the columns to add from `table`.
+    #' @return A TableHandle referencing the new table.
+    join = function(table, on = character(), joins = character()) {
       verify_string("on", on, FALSE)
       verify_string("joins", joins, FALSE)
-      return(TableHandle$new(self$.internal_rcpp_object$cross_join(
+      return(TableHandle$new(self$.internal_rcpp_object$join(
         table$.internal_rcpp_object,
         on, joins
       )))
@@ -406,6 +414,7 @@ TableHandle <- R6Class("TableHandle",
     #' @param table TableHandle referencing the table to join with.
     #' @param on String or list of strings denoting the names of the columns to join on.
     #' @param joins String or list of strings denoting the names of the columns to add from `table`.
+    #' @return A TableHandle referencing the new table.
     natural_join = function(table, on = character(), joins = character()) {
       verify_string("on", on, FALSE)
       verify_string("joins", joins, FALSE)
@@ -422,6 +431,7 @@ TableHandle <- R6Class("TableHandle",
     #' @param table TableHandle referencing the table to join with.
     #' @param on String or list of strings denoting the names of the columns to join on.
     #' @param joins String or list of strings denoting the names of the columns to add from `table`.
+    #' @return A TableHandle referencing the new table.
     exact_join = function(table, on = character(), joins = character()) {
       verify_string("on", on, FALSE)
       verify_string("joins", joins, FALSE)

R/rdeephaven/inst/tests/testthat/test_table_ops.R

@@ -768,11 +768,11 @@ test_that("sort behaves as expected", {
   data$client$close()
 })
 
-test_that("cross_join behaves as expected", {
+test_that("join behaves as expected", {
   data <- setup()
 
   new_th1 <- data$th5$
-    cross_join(data$th6,
+    join(data$th6,
       on = character(),
       joins = c("X_y = X", "Y_y = Y", "Number1_y = Number1", "Number2_y = Number2")
     )

R/rdeephaven/src/client.cpp

@@ -550,7 +550,7 @@ RCPP_MODULE(DeephavenInternalModule) {
     .method("percentile_by", &TableHandleWrapper::PercentileBy)
     .method("count_by", &TableHandleWrapper::CountBy)
 
-    .method("cross_join", &TableHandleWrapper::CrossJoin)
+    .method("join", &TableHandleWrapper::CrossJoin)
     .method("natural_join", &TableHandleWrapper::NaturalJoin)
     .method("exact_join", &TableHandleWrapper::ExactJoin)