[GitHub] [arrow] praveenbingo commented on a change in pull request #8231: ARROW-10023: [C++][Gandiva] Implement split_part function in gandiva

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

praveenbingo commented on a change in pull request #8231:
URL: https://github.com/apache/arrow/pull/8231#discussion_r498103645



##########
File path: cpp/src/gandiva/precompiled/string_ops.cc
##########
@@ -40,6 +40,18 @@ gdv_int32 bit_length_binary(const gdv_binary input, gdv_int32 length) {
   return length * 8;
 }
 
+int match_string(const char* input, gdv_int32 input_len, gdv_int32 start_pos,

Review comment:
       please force inline..

##########
File path: cpp/src/gandiva/precompiled/string_ops.cc
##########
@@ -40,6 +40,18 @@ gdv_int32 bit_length_binary(const gdv_binary input, gdv_int32 length) {
   return length * 8;
 }
 
+int match_string(const char* input, gdv_int32 input_len, gdv_int32 start_pos,

Review comment:
       are we intentionally not inling this?

##########
File path: cpp/src/gandiva/precompiled/string_ops.cc
##########
@@ -835,6 +847,66 @@ const char* replace_utf8_utf8_utf8(gdv_int64 context, const char* text,
                                              out_len);
 }
 
+FORCE_INLINE
+const char* split_part(gdv_int64 context, const char* text, gdv_int32 text_len,
+                       const char* delimiter, gdv_int32 delim_len, gdv_int32 index,
+                       gdv_int32* out_len) {
+  if (index < 1) {
+    char error_message[100];
+    snprintf(error_message, sizeof(error_message),
+             "Index in split_part must be positive, value provided was %d", index);
+    gdv_fn_context_set_error_msg(context, error_message);
+    *out_len = 0;
+    return "";
+  }
+
+  if (delim_len == 0 || text_len == 0) {
+    // output will just be text if no delimiter is provided
+    *out_len = text_len;
+    return text;
+  }
+
+  int i = 0, match_no = 1;
+
+  while (i < text_len) {
+    // find the position where delimiter matched for the first time
+    int match_pos = match_string(text, text_len, i, delimiter, delim_len);
+    if (match_pos == -1 && match_no != index) {
+      // reached the end without finding a match.
+      *out_len = 0;
+      return "";
+    } else {
+      // Found a match. If the match number is index then return this match
+      if (match_no == index) {
+        int end_pos = match_pos - delim_len;
+
+        if (match_pos == -1) {
+          // end position should be last position of the string as we have the last
+          // delimiter
+          end_pos = text_len;
+        }
+
+        *out_len = end_pos - i;
+        char* out_str =
+            reinterpret_cast<char*>(gdv_fn_context_arena_malloc(context, *out_len));
+        if (out_str == nullptr) {
+          gdv_fn_context_set_error_msg(context,
+                                       "Could not allocate memory for output string");
+          *out_len = 0;

Review comment:
       intialize this to 0 in the beginning and only override in the positive case? avoids missing setting this value for e.g. the last return misses this i guess?




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