fix: Refactor marker in Neo4jStalenessRemovalTask

[otakart]

Summary of Changes

When milliseconds_to_expire is used to identify stale data, Neo4jStalenessRemovalTask passes marker with expression (timestamp() - {}).format(milliseconds_to_expire) as parameter to neo4j. Arbitrary expressions as parameters are not supported by neo4j.

This PR gets timestamp() value from neo4j and calculates marker as integer.

Tests

Modified tests/unit/task/test_neo4j_staleness_removal_task.py.

CheckList

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[codecov-commenter]

Codecov Report

Merging #297 into master will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #297      +/-   ##
==========================================
+ Coverage   73.45%   73.57%   +0.12%     
==========================================
  Files         103      103              
  Lines        4328     4329       +1     
  Branches      403      403              
==========================================
+ Hits         3179     3185       +6     
+ Misses       1049     1044       -5     
  Partials      100      100              

Impacted Files	Coverage Δ
databuilder/task/neo4j_staleness_removal_task.py	89.25% <100.00%> (+4.25%)	⬆️

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[feng-tao]

hey @jinhyukchang could you take a look at this pr? thanks.

[jinhyukchang]

@otakart Could you elaborate what you meant by "Arbitrary expressions as parameters are not supported by neo4j."? This is working in our Neo4j version "3.3.5", but I wonder if it's not working for you.

[otakart]

Hi @jinhyukchang ,
Thanks for checking the PR.
My motivation is that staleness removal was not working for me with MS_TO_EXPIRE. It was working fine with JOB_PUBLISH_TAG, but I need to identify stale records by age. I'm using neo4j version 3.3.9.

According to neo4j documentation https://neo4j.com/docs/cypher-manual/3.5/syntax/parameters/
there is a limited set of use cases for parameters. In MS_TO_EXPIRE case the parameter marker passed to neo4j is 'timestamp() - 1234' (where 1234 is value of MS_TO_EXPIRE) and this is interpreted as string literal by neo4j. It can be checked by running simple script:

from neo4j import GraphDatabase

host = '***'
user = '***'
pw = '***'

driver = GraphDatabase.driver(host, auth=(user, pw))
with driver.session() as session:
    res = session.run('return $param as result', param='timestamp() - 123')
    print(res.single())

the output is:

<Record result='timestamp() - 123'>

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[otakart]

Hi @jinhyukchang please let me know if you need any additional information. Thanks

[feng-tao]

ping @jinhyukchang

[feng-tao]

@otakart if you update the pr, I will take a look and merge it given @jinhyukchang is not available. Sorry for the wait

[otakart]

@feng-tao it looks like the issue has been solved by PR #307. So we can close this PR. Thanks