GH-51395: [C++][Docs] Replace RapidJSON with simdjson in row converter example by Reranko05 · Pull Request #51396 · apache/arrow

Reranko05 · 2026-09-19T19:44:20Z

Rationale for this change

This PR continues the simdjson migration by replacing RapidJSON usage in the C++ row converter example with simdjson and Arrow's existing JsonWriter.

Changes

Replace RapidJSON DOM parsing with simdjson's DOM API.
Replace RapidJSON JSON generation with Arrow's JsonWriter.
Preserve the existing row-to-Arrow and Arrow-to-row conversion flow.
Update the example to link against arrow::simdjson.

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GitHub Issue: [C++][Docs] Replace RapidJSON with simdjson in row converter example #51395

Reranko05 · 2026-09-20T18:48:59Z

Will mark this PR Ready to Review after #51038 is merged.

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pitrou · 2026-10-08T15:36:48Z

+//  * arrow::TableBatchReader and Arrow iterators for converting Arrow tables back
+//    into row-based JSON data
+
+namespace arrow {


Example code shouldn't be in the arrow namespace because it showcases how third-party code using Arrow C++ could look like.

Ah, okay. I got it.

pitrou · 2026-10-08T15:37:01Z

+//  * arrow::internal::JsonWriter for writing JSON values
+//  * arrow::internal::ParseJsonObject and related helpers for parsing JSON


Examples should not use any internal Arrow APIs.

Okay, understood.

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Reranko05 · 2026-10-11T09:52:15Z

I have not got the time to review this myself after changing it into plain simdjson. I will mark it as Ready for review after I review this.

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Reranko05 · 2026-10-16T11:20:48Z

@pitrou @kou Could you review this when you have time? (CI failures seem unrelated)

kou · 2026-10-16T13:58:11Z

+  // Parse each row and append its values to the corresponding Arrow builders.
+  for (const auto& json : rows) {
+    ARROW_ASSIGN_OR_RAISE(auto element,
+                          Unwrap(parser.parse(json), "Failed to parse JSON row"));
+    ARROW_ASSIGN_OR_RAISE(auto object,
+                          Unwrap(element.get_object(), "Expected a JSON object"));
+
+    for (int i = 0; i < schema->num_fields(); ++i) {
+      const auto& field = schema->field(i);
+      arrow::ArrayBuilder* builder = batch_builder->GetField(i);
+
+      ARROW_ASSIGN_OR_RAISE(auto value, GetField(object, field->name()));
+
+      if (!value.has_value()) {
+        ARROW_RETURN_NOT_OK(builder->AppendNull());
+      } else {
+        ARROW_RETURN_NOT_OK(AppendJsonValue(*value, field->type(), builder));
+      }
+    }
+  }


Can we keep column based iteration (not row based iteration) like the RapidJSON version so that we demonstrate how to use a visitor to convert row based data to Arrow data?

I changed the impl to do column based iteration.

kou · 2026-10-16T14:03:30Z

+  for (int64_t i = 0; i < batch->num_rows(); ++i) {
+    ARROW_ASSIGN_OR_RAISE(auto row, ConvertRowToJson(*batch, i));
+    rows.push_back(std::make_shared<std::string>(std::move(row)));
+  }


Can we keep column based iteration (not row based iteration) like the RapidJSON version so that we demonstrate how to use a visitor to convert Arrow data to row based data?

As said above.

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Reranko05 · 2026-10-16T18:01:34Z

I have not updated the docs yet, once the impl is approved I will update the docs accordingly.

github-actions Bot added Component: C++ awaiting review Awaiting review labels Sep 19, 2026

Reranko05 added the CI: Extra: C++ Run extra C++ CI label Sep 19, 2026

Reranko05 changed the title ~~GH-51395: [C++] Replace RapidJSON with Simdjson in row converter example~~ GH-51395: [C++] Replace RapidJSON with simdjson in row converter example Sep 19, 2026

Reranko05 force-pushed the example-doc branch from 3842058 to 9813fc2 Compare September 19, 2026 20:23

github-actions Bot added the Component: Documentation label Sep 19, 2026

Reranko05 changed the title ~~GH-51395: [C++] Replace RapidJSON with simdjson in row converter example~~ GH-51395: [C++][Docs] Replace RapidJSON with simdjson in row converter example Sep 19, 2026

Reranko05 added 4 commits October 8, 2026 13:14

Replace example

1f15ba4

Update rst doc

503d318

Minor fixes

353bfa8

Self Review

4934519

Reranko05 force-pushed the example-doc branch from ebf072f to 4934519 Compare October 8, 2026 08:29

Reranko05 marked this pull request as ready for review October 8, 2026 09:37

Reranko05 requested a review from pitrou as a code owner October 8, 2026 09:37

Copilot AI balanced review requested due to automatic review settings October 8, 2026 09:37

Copilot AI reviewed Oct 8, 2026

Reranko05 requested a review from kou October 8, 2026 09:37

pitrou reviewed Oct 8, 2026

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github-actions Bot added awaiting committer review Awaiting committer review and removed awaiting review Awaiting review labels Oct 8, 2026

Copilot AI balanced review requested due to automatic review settings October 9, 2026 09:20

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Use plain simdjson

7b885c3

Copilot AI balanced review requested due to automatic review settings October 9, 2026 09:40

Reranko05 force-pushed the example-doc branch from 84ed127 to 7b885c3 Compare October 9, 2026 09:40

Copilot AI reviewed Oct 9, 2026

Reranko05 marked this pull request as draft October 11, 2026 09:52

Add get_uint64()

6993fd2

Reranko05 marked this pull request as ready for review October 16, 2026 11:19

Copilot AI balanced review requested due to automatic review settings October 16, 2026 11:19

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kou reviewed Oct 16, 2026

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github-actions Bot added awaiting changes Awaiting changes and removed awaiting committer review Awaiting committer review labels Oct 16, 2026

Change to column based iteration

75fc21a

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github-actions Bot added awaiting change review Awaiting change review and removed awaiting changes Awaiting changes labels Oct 16, 2026

		// * arrow::internal::JsonWriter for writing JSON values
		// * arrow::internal::ParseJsonObject and related helpers for parsing JSON

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Reranko05 commented Sep 19, 2026 •

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