[GitHub] [arrow] thisisnic commented on a change in pull request #10191: ARROW-12731: [R] Use InMemoryDataset for Table/RecordBatch in dplyr code

[GitBox <gi...@apache.org>]

thisisnic commented on a change in pull request #10191:
URL: https://github.com/apache/arrow/pull/10191#discussion_r631290976



##########
File path: r/R/dplyr-functions.R
##########
@@ -0,0 +1,352 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+
+#' @include expression.R
+NULL
+
+# This environment is an internal cache for things including data mask functions
+# We'll populate it at package load time.
+.cache <- NULL
+init_env <- function () {
+  .cache <<- new.env(hash = TRUE)
+}
+init_env()
+
+# nse_funcs is a list of functions that operated on (and return) Expressions
+# These will be the basis for a data_mask inside dplyr methods
+# and will be added to .cache at package load time
+
+# Start with mappings from R function name spellings
+nse_funcs <- lapply(set_names(names(.array_function_map)), function(operator) {
+  force(operator)
+  function(...) build_expr(operator, ...)
+})
+
+# Now add functions to that list where the mapping from R to Arrow isn't 1:1
+# Each of these functions should have the same signature as the R function
+# they're replacing.
+#
+# When to use `build_expr()` vs. `Expression$create()`?
+#
+# Use `build_expr()` if you need to
+# (1) map R function names to Arrow C++ functions
+# (2) wrap R inputs (vectors) as Array/Scalar
+#
+# `Expression$create()` is lower level. Most of the functions below use it
+# because they manage the preparation of the user-provided inputs
+# and don't need to wrap scalars
+
+nse_funcs$cast <- function(x, target_type, safe = TRUE, ...) {
+  opts <- cast_options(safe, ...)
+  opts$to_type <- as_type(target_type)
+  Expression$create("cast", x, options = opts)
+}
+
+nse_funcs$dictionary_encode <- function(x,
+                                        null_encoding_behavior = c("mask", "encode")) {
+  behavior <- toupper(match.arg(null_encoding_behavior))
+  null_encoding_behavior <- NullEncodingBehavior[[behavior]]
+  Expression$create(
+    "dictionary_encode",
+    x,
+    options = list(null_encoding_behavior = null_encoding_behavior)
+  )
+}
+
+nse_funcs$between <- function(x, left, right) {
+  x >= left & x <= right
+}
+
+# as.* type casting functions
+# as.factor() is mapped in expression.R
+nse_funcs$as.character = function(x) {
+  Expression$create("cast", x, options = cast_options(to_type = string()))
+}
+nse_funcs$as.double = function(x) {
+  Expression$create("cast", x, options = cast_options(to_type = float64()))
+}
+nse_funcs$as.integer = function(x) {
+  Expression$create(
+    "cast",
+    x,
+    options = cast_options(
+      to_type = int32(),
+      allow_float_truncate = TRUE,
+      allow_decimal_truncate = TRUE
+    )
+  )
+}
+nse_funcs$as.integer64 = function(x) {
+  Expression$create(
+    "cast",
+    x,
+    options = cast_options(
+      to_type = int64(),
+      allow_float_truncate = TRUE,
+      allow_decimal_truncate = TRUE
+    )
+  )
+}
+nse_funcs$as.logical = function(x) {
+  Expression$create("cast", x, options = cast_options(to_type = boolean()))
+}
+nse_funcs$as.numeric = function(x) {
+  Expression$create("cast", x, options = cast_options(to_type = float64()))
+}
+
+# String functions
+nse_funcs$nchar = function(x, type = "chars", allowNA = FALSE, keepNA = NA) {
+  if (allowNA) {
+    arrow_not_supported("allowNA = TRUE")
+  }
+  if (is.na(keepNA)) {
+    keepNA <- !identical(type, "width")
+  }
+  if (!keepNA) {
+    # TODO: I think there is a fill_null kernel we could use, set null to 2
+    arrow_not_supported("keepNA = TRUE")
+  }
+  if (identical(type, "bytes")) {
+    Expression$create("binary_length", x)
+  } else {
+    Expression$create("utf8_length", x)
+  }
+}
+
+nse_funcs$str_trim = function(string, side = c("both", "left", "right")) {
+  side <- match.arg(side)
+  trim_fun <- switch(side,
+    left = "utf8_ltrim_whitespace",
+    right = "utf8_rtrim_whitespace",
+    both = "utf8_trim_whitespace"
+  )
+  Expression$create(trim_fun, string)
+}
+
+nse_funcs$grepl <- function(pattern, x, ignore.case = FALSE, fixed = FALSE) {
+  arrow_fun <- ifelse(fixed && !ignore.case, "match_substring", "match_substring_regex")
+  Expression$create(
+    arrow_fun,
+    x,
+    options = list(pattern = format_string_pattern(pattern, ignore.case, fixed))
+  )
+}

Review comment:
       Compared to the previous way of defining these functions, this is a lot simpler to understand, nice!




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