felixcheung commented on a change in pull request #23184: [SPARK-26227][R]
from_[csv|json] should accept schema_of_[csv|json] in R API
URL: https://github.com/apache/spark/pull/23184#discussion_r243923328
##########
File path: R/pkg/R/functions.R
##########
@@ -2328,22 +2343,27 @@ setMethod("schema_of_json", signature(x =
"characterOrColumn"),
#' If the string is unparseable, the Column will contain the value NA.
#'
#' @rdname column_collection_functions
-#' @aliases from_csv from_csv,Column,character-method
+#' @aliases from_csv from_csv,Column,characterOrstructTypeOrColumn-method
#' @examples
#'
#' \dontrun{
-#' df <- sql("SELECT 'Amsterdam,2018' as csv")
+#' csv <- "Amsterdam,2018"
+#' df <- sql(paste0("SELECT '", csv, "' as csv"))
#' schema <- "city STRING, year INT"
-#' head(select(df, from_csv(df$csv, schema)))}
+#' head(select(df, from_csv(df$csv, schema)))
+#' head(select(df, from_csv(df$csv, structType(schema))))
+#' head(select(df, from_csv(df$csv, schema_of_csv(csv))))}
#' @note from_csv since 3.0.0
-setMethod("from_csv", signature(x = "Column", schema = "characterOrColumn"),
+setMethod("from_csv", signature(x = "Column", schema =
"characterOrstructTypeOrColumn"),
function(x, schema, ...) {
- if (class(schema) == "Column") {
- jschema <- schema@jc
- } else if (is.character(schema)) {
+ if (class(schema) == "structType") {
+ schema <- callJMethod(schema$job, "toDDL")
+ }
+
+ if (is.character(schema)) {
jschema <- callJStatic("org.apache.spark.sql.functions", "lit",
schema)
Review comment:
hmm, why in the case for from_json, if schema is character is
`structType(schema)$jobj`
where for from_csv, is `callJStatic("org.apache.spark.sql.functions", "lit",
schema)`
?
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