Enable `.nt` file storage (hashtag2814)

[vikramsubramanian]

N-Triples files are valid Turtle files. They are the simplest of RDF formats where each triple is written one one line and without any prefix or base directives/shortening (so each IRI is written as full IRIs) and no grouping of triples by subject as in Turtle. Currently if I do this, I get an error:

kuzu> copy wklx from "/home/lc/Developer/semih/rdf-data/wiki-data/latest-lexemes-nt.nt";
Error: Copy exception: Unsupported file type .nt

However if I rename the file to latest-lexemes-nt.ttl then the loading works. I also tested that the Turtle and N-Triple version of the latest Wikidata lexemes dataset gives similar counts (not exact but very close).
)

[mayil-ai[bot]]

Summary: Unable to copy .nt file for storage, but works when renamed to .ttl.

Possible Solution

Based on the provided information, the issue is that the Kùzu database system does not recognize .nt (N-Triples) files as a supported RDF format when using the copy command, even though it should. The workaround of renaming .nt files to .ttl (Turtle) suggests that the system supports Turtle files but not N-Triples, despite both being valid RDF formats.

To resolve the issue:

• Locate the part of the code that implements the copy command.
• Within the copy command implementation, find where the file extension is being validated.
• Update the file extension validation logic to include .nt as a supported file type for RDF data.
• Ensure that the RDF parsing logic can handle the N-Triples format. This may involve checking the RDF parser (possibly the Serd library, as seen in third_party/serd/src/n3.c and third_party/serd/src/writer.c) to confirm it supports .nt files.
• If the parser supports N-Triples, ensure that the copy command correctly invokes the parser for .nt files.
• If the parser does not support N-Triples, you may need to update the parser or use a different library that supports all required RDF formats.
• Add or update unit tests to cover the loading of .nt files to prevent regressions in the future.

Note: The provided code snippets do not contain the exact location where the copy command is implemented or where the file extension validation occurs. You will need to search the codebase for the relevant sections to apply the above solution.

Code snippets to check

• third_party/serd/src/writer.c

  This file contains code for writing N-Triples, which is relevant to enabling '.nt' file storage.

• third_party/serd/src/n3.c

  This file contains code for parsing RDF syntaxes, which may need to be reviewed to ensure '.nt' files are supported.

• src/include/common/keyword/rdf_keyword.h

  This file contains RDF-related keywords and may need to be updated to include '.nt' file support.