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Remove FOR UPDATE SKIP LOCKED from job locking sql statement #288

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Jun 30, 2021
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Remove FOR UPDATE SKIP LOCKED from job locking sql statement #288

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6 changes: 0 additions & 6 deletions lib/good_job/lockable.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -48,15 +48,9 @@ module Lockable
end

composed_cte = Arel::Nodes::As.new(cte_table, Arel::Nodes::SqlLiteral.new([cte_type, "(", cte_query.to_sql, ")"].join(' ')))

# In addition to an advisory lock, there is also a FOR UPDATE SKIP LOCKED
# because this causes the query to skip jobs that were completed (and deleted)
# by another session in the time since the table snapshot was taken.
# In rare cases under high concurrency levels, leaving this out can result in double executions.
query = cte_table.project(cte_table[:id])
.with(composed_cte)
.where(Arel.sql(sanitize_sql_for_conditions(["#{function}(('x' || substr(md5(:table_name || #{connection.quote_table_name(cte_table.name)}.#{connection.quote_column_name(column)}::text), 1, 16))::bit(64)::bigint)", { table_name: table_name }])))
.lock(Arel.sql("FOR UPDATE SKIP LOCKED"))

limit = original_query.arel.ast.limit
query.limit = limit.value if limit.present?
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2 changes: 0 additions & 2 deletions spec/lib/good_job/lockable_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,6 @@
FROM "rows"
WHERE pg_try_advisory_lock(('x' || substr(md5('good_jobs' || "rows"."id"::text), 1, 16))::bit(64)::bigint)
LIMIT 2
FOR UPDATE SKIP LOCKED
)
ORDER BY "good_jobs"."priority" DESC
SQL
Expand All @@ -58,7 +57,6 @@
FROM "rows"
WHERE pg_try_advisory_lock(('x' || substr(md5('good_jobs' || "rows"."queue_name"::text), 1, 16))::bit(64)::bigint)
LIMIT 2
FOR UPDATE SKIP LOCKED
)
ORDER BY "good_jobs"."priority" DESC
SQL
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