[GitHub] [arrow] pitrou commented on a change in pull request #10454: ARROW-12950: [C++] Add count_substring kernel

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

pitrou commented on a change in pull request #10454:
URL: https://github.com/apache/arrow/pull/10454#discussion_r646747304



##########
File path: cpp/src/arrow/compute/kernels/scalar_string_test.cc
##########
@@ -91,6 +91,25 @@ TYPED_TEST(TestBinaryKernels, FindSubstring) {
   MatchSubstringOptions options_double_char_2{"bbcaa"};
   this->CheckUnary("find_substring", R"(["abcbaabbbcaabccabaab"])", this->offset_type(),
                    "[7]", &options_double_char_2);
+
+  MatchSubstringOptions options_empty{""};
+  this->CheckUnary("find_substring", R"(["", "a", null])", this->offset_type(),
+                   "[0, 0, null]", &options_empty);
+}
+
+TYPED_TEST(TestBinaryKernels, CountSubstring) {
+  MatchSubstringOptions options{"aba"};
+  this->CheckUnary("count_substring", "[]", this->offset_type(), "[]", &options);
+  this->CheckUnary(
+      "count_substring",
+      R"(["", null, "ab", "aba", "baba", "ababa", "abaaba", "babacaba", "ABA"])",
+      this->offset_type(), "[0, null, 0, 1, 1, 1, 2, 2, 0]", &options);
+
+  MatchSubstringOptions options_empty{""};
+  this->CheckUnary("count_substring", R"(["", null, "abc"])", this->offset_type(),
+                   "[1, null, 4]", &options_empty);
+
+  // TODO: case-insensitive

Review comment:
       I'd like to see a more challenging use case, e.g. counting the number of occurrences of `"aa"` in `"aaaaa"`.




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