graph: fix inefficient query for IsPublicNode

[Abdulkbk]

fixes #10337 (partially)

Change Description

In this PR, we rewrite the query for IsPublicV1Node, which returns a boolean based on if a node has a public or private channel. This particularly fixes an issue sqlite backend as it struggles to efficiently use multiple indexes across seperate columns in one query.

Step to test

cd graph/db

go test -tags test_db_sqlite  -run TestNodeIsPublic -v # ensure we still correctly distinguish between pub & priv

[gemini-code-assist]

Summary of Changes

Hello @Abdulkbk, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a significant performance bottleneck in the IsPublicV1Node query, which was particularly inefficient for sqlite databases due to its struggle with complex OR conditions across multiple indexed columns. By restructuring the query to use UNION ALL, the change optimizes how the database utilizes indexes, leading to more efficient execution and resolving the identified performance issue.

Highlights

• Query Optimization: The IsPublicV1Node query has been rewritten to improve its efficiency, specifically targeting performance issues with the sqlite backend.
• SQL Query Refactoring: The original query's OR condition across joined tables (n.id = c.node_id_1 OR n.id = c.node_id_2) has been refactored into two separate SELECT statements combined with UNION ALL. This change allows for better utilization of database indexes.
• Dependency Management: A local replace directive for github.com/lightningnetwork/lnd/sqldb has been added to go.mod, pointing to the local sqldb directory.

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[gemini-code-assist]

Code Review

This pull request refactors the IsPublicV1Node SQL query to improve performance, particularly for the SQLite backend. The change replaces an OR condition in a JOIN with a UNION ALL construct, which is a sound optimization strategy to help the query planner use indexes more effectively. The change is logical and well-explained. I have one minor suggestion regarding SQL formatting to ensure consistency.

[ziggie1984]

can you create some stress tests to see whether union is actually better ?

[Abdulkbk]

can you create some stress tests to see whether union is actually better ?

I added a benchmark as the first commit, the following is what I found after running:

go test -tags=test_db_sqlite -bench=BenchmarkIsPublicNode  > sqlite_or.txt

# then

go test -tags=test_db_sqlite -bench=BenchmarkIsPublicNode  > sqlite_union.txt

# finally
benchstat sqlite_or.txt sqlite_union.txt 

Query Type	Iterations (b.N)	Time per op (ns/op)
UNION ALL	388	3,009,488 ns/op (~3ms)
OR	289	4,063,903 ns/op (~4ms)

The fact that this benchmark is run with approximately 8k nodes means that, if the number of nodes is increased to around ~80k, the difference will become more noticeable.