Fix Memgraph parameter serialization error for cited_by_count_date

[ssheikholeslami]

Summary

• Change cited_by_count_date type from Optional[datetime] to Optional[int] in AnonymousArticle model

Problem

When ingesting DOIs, the Article.save() query fails with:
Memgraph.ExecutionException - Couldn't read parameters!

The root cause is a type mismatch:

• parser.py passes datetime.now().year which is an int (e.g. 2026)
• The model declares cited_by_count_date: Optional[datetime]
• Pydantic converts the int into a datetime object (interpreting it as a Unix timestamp)
• The Neo4j driver serializes this as a Bolt temporal type
• Memgraph cannot deserialize the temporal type parameter

Fix

Changed the type annotation in models.py to Optional[int], which matches the actual usage. The field only stores the year the citation count was fetched, not a full datetime.

Test plan

• Run research_index list_of_dois.csv -l 5 — DOIs ingested without errors
• Verify Memgraph logs show no Couldn't read parameters! errors
• Run hatch test — all tests pass

[Copilot]

Pull request overview

Fixes Memgraph parameter serialization failures by aligning the cited_by_count_date field type with actual usage (year integer) so the Neo4j driver doesn’t send a Bolt temporal parameter that Memgraph can’t deserialize.

Changes:

• Change AnonymousArticle.cited_by_count_date from Optional[datetime] to Optional[int].

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[Copilot]

cited_by_count_date now stores a year integer rather than a full date/time, so the field name is misleading and can cause confusion for future readers/DB consumers. Consider renaming it to something like cited_by_count_year (and, if you need to keep the persisted property name stable, use a Pydantic alias or a clear field description).

Suggested change

	cited_by_count_date: Optional[int] = None
	cited_by_count_year: Optional[int] = Field(
	default=None,
	alias="cited_by_count_date",
	description="Year associated with cited_by_count; persisted as 'cited_by_count_date'.",
	)

[willu47]

Looks good @ssheikholeslami

I'd recommend changing the name as the CoPilot bot has recommended - cited_by_count_date should really be cited_by_count_year. However, this may have downstream effects on the research_index API and the memgraph database schema.

If you want to leave it for later, I suggest creating an issue and merging this as is.