Github user mattpollock commented on a diff in the pull request:
https://github.com/apache/spark/pull/9012#discussion_r42755365
--- Diff: R/pkg/R/DataFrame.R ---
@@ -1457,15 +1457,142 @@ setMethod("join",
dataFrame(sdf)
})
-#' @rdname merge
+#'
#' @name merge
#' @aliases join
+#' @title Merges two data frames
+#' @param x the first data frame to be joined
+#' @param y the second data frame to be joined
+#' @param by a character vector specifying the join columns. If by is not
+#' specified, the common column names in \code{x} and \code{y} will be
used.
+#' @param by.x a character vector specifying the joining columns for x.
+#' @param by.y a character vector specifying the joining columns for y.
+#' @param all.x a boolean value indicating whether all the rows in x should
+#' be including in the join
+#' @param all.y a boolean value indicating whether all the rows in y should
+#' be including in the join
+#' @param sort a logical argument indicating whether the resulting columns
should be sorted
+#' @details If all.x and all.y are set to FALSE, a natural join will be
returned. If
+#' all.x is set to TRUE and all.y is set to FALSE, a left outer join will
+#' be returned. If all.x is set to FALSE and all.y is set to TRUE, a
right
+#' outer join will be returned. If all.x and all.y are set to TRUE, a
full
+#' outer join will be returned.
+#' @rdname merge
+#' @export
+#' @examples
+#'\dontrun{
+#' sc <- sparkR.init()
+#' sqlContext <- sparkRSQL.init(sc)
+#' df1 <- jsonFile(sqlContext, path)
+#' df2 <- jsonFile(sqlContext, path2)
+#' merge(df1, df2) # Performs a Cartesian
+#' merge(df1, df2, by = "col1") # Performs an inner join based on
expression
+#' merge(df1, df2, by.x = "col1", by.y = "col2", all.y = TRUE)
+#' merge(df1, df2, by.x = "col1", by.y = "col2", all.x = TRUE)
+#' merge(df1, df2, by.x = "col1", by.y = "col2", all.x = TRUE, all.y =
TRUE)
+#' merge(df1, df2, by.x = "col1", by.y = "col2", all = TRUE, sort = FALSE)
+#' merge(df1, df2, by = "col1", all = TRUE, suffixes = c("-X", "-Y"))
+#' }
setMethod("merge",
signature(x = "DataFrame", y = "DataFrame"),
- function(x, y, joinExpr = NULL, joinType = NULL, ...) {
- join(x, y, joinExpr, joinType)
- })
+ function(x, y, by = intersect(names(x), names(y)), by.x = by,
by.y = by,
+ all = FALSE, all.x = all, all.y = all,
+ sort = TRUE, suffixes = c("_x","_y"), ... ) {
--- End diff --
Will the default behavior of `merge(x, y, by="colname")` be to return a DF
where the join key column is not present? Looking at lines 1533 & 1534 below it
looks like the resulting DF will contain "colname_x" and "colname_y", but not
"colname". My preference would be to drop `y$colname` after the join however a
quick fix might be to set the default `suffixes` param to `suffixes = c("",
"_y")`
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