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new b0d4f1bf feat(docs): how to process graph data with labels (#643)
b0d4f1bf is described below
commit b0d4f1bf46381015c17df6c0747dcc3282529431
Author: Elssky <[email protected]>
AuthorDate: Mon Oct 28 11:13:42 2024 +0800
feat(docs): how to process graph data with labels (#643)
---
docs/libraries/cpp/getting-started.md | 99 +++++++++++++++++++++++++++++++++++
1 file changed, 99 insertions(+)
diff --git a/docs/libraries/cpp/getting-started.md
b/docs/libraries/cpp/getting-started.md
index cf93f75b..c2c433fd 100644
--- a/docs/libraries/cpp/getting-started.md
+++ b/docs/libraries/cpp/getting-started.md
@@ -277,6 +277,105 @@ is used to write the results to new generated data chunks.
Please refer to [more examples](examples/out-of-core.md) to learn
about the other available case studies utilizing GraphAr.
+### Processing Graph Data with Labels
+
+As GraphAr supports LPG data, users can add labels for vertices and use
related label filtering functions to obtain specified vertices.
+The standard csv format of graph data with labels supported by GraphAr is
`id|:LABEL|property_1|property_2`, if a vertex has multiple labels, use ; to
separate them. Here is an example.
+
+```csv
+id|:LABEL|name|url
+0|company;public|Kam_Air|http://dbpedia.org/resource/Kam_Air
+1|company|Balkh_Airlines|http://dbpedia.org/resource/Balkh_Airlines
+2|company|Khyber_Afghan_Airlines|http://dbpedia.org/resource/Khyber_Afghan_Airlines
+
+```
+
+When you have the data ready, you can read the file into `arrow::Table` by
using arrow IO function.
+
+``` cpp
+ arrow::csv::ReadOptions read_options{};
+ arrow::csv::ParseOptions parse_options{};
+ arrow::csv::ConvertOptions convert_options{};
+
+ parse_options.delimiter = '|';
+
+ auto input = arrow::io::ReadableFile::Open(test_data_dir +
"/ldbc/organisation_0_0.csv", arrow::default_memory_pool()).ValueOrDie();
+
+ auto reader = arrow::csv::TableReader::Make(
+ arrow::io::default_io_context(),
+ input,
+ read_options,
+ parse_options,
+ convert_options).ValueOrDie();
+
+ std::shared_ptr<arrow::Table> table;
+ table = reader->Read().ValueOrDie();
+```
+You can export label table to disk in parquet format, and read it back into
memory in the following way.
+``` cpp
+ // write arrow table as parquet chunk
+ auto maybe_writer =
+ VertexPropertyWriter::Make(vertex_info, test_data_dir +
"/ldbc/parquet/");
+ REQUIRE(!maybe_writer.has_error());
+ auto writer = maybe_writer.value();
+ REQUIRE(writer->WriteTable(table, 0).ok());
+ REQUIRE(writer->WriteVerticesNum(table->num_rows()).ok());
+
+ // read parquet chunk as arrow table
+ auto maybe_reader =
+ VertexPropertyArrowChunkReader::Make(graph_info, "organisation", labels);
+ assert(maybe_reader.status().ok());
+ auto reader = maybe_reader.value();
+ assert(reader->seek(0).ok());
+ assert(reader->GetLabelChunk().status().ok());
+ assert(reader->next_chunk().ok());
+```
+### Using Label Filtering Functions
+
+By calling the `graphar::VerticesCollection::verticesWithLabel` or
`graphar::VerticesCollection::verticesWithMultipleLabels` API, we can specify a
certain type of vertices on a certain graph, then filter out all vertices that
match one or more labels. Here we introduce several examples of using label
filtering.
+
+
+
+```cpp
+ graph_info = ...
+ auto vertex_info = graph_info->GetVertexInfo("organisation");
+ auto labels = vertex_info->GetLabels();
+
+ // query vertices with a specific label
+ auto maybe_filter_vertices_collection =
+ graphar::VerticesCollection::verticesWithLabel(std::string("company"),
graph_info, type);
+ ASSERT(!maybe_filter_vertices_collection.has_error());
+ auto filter_vertices = maybe_filter_vertices_collection.value();
+
+ // iterate vertices with label "company"
+ for (auto it = filter_vertices->begin(); it != filter_vertices->end();
+ ++it) {
+ // get a node's all labels
+ auto label_result = it.label();
+ std::cout << "id: " << it.id() << " ";
+ if (!label_result.has_error()) {
+ for (auto label : label_result.value()) {
+ std::cout << label << " ";
+ }
+ }
+ // ...
+ }
+
+ // query vertices based on a query result
+ auto maybe_filter_vertices_collection =
+ graphar::VerticesCollection::verticesWithLabel(std::string("public"),
+ filter_vertices);
+
+ // query vertices with multi labels
+ auto maybe_filter_vertices_collection =
+ graphar::VerticesCollection::verticesWithMultipleLabels({"company",
"public"}, graph_info, type);
+ // ...
+
+
+```
+Notice that, if the first two queries are executed successively, the result is
equivalent to the third query.
+
+
### Working with Cloud Storage (S3, OSS)
GraphAr supports reading and writing data from and to cloud storage, including
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