83 lines
3.1 KiB
Ruby
83 lines
3.1 KiB
Ruby
class DelayedJobsUseAdvisoryLocks < ActiveRecord::Migration
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tag :predeploy
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def self.connection
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Delayed::Backend::ActiveRecord::Job.connection
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end
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def self.up
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# use an advisory lock based on the name of the strand, instead of locking the whole table
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# note that we're using half of the md5, so collisions are possible, but we don't really
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# care because that would just be the old behavior, whereas for the most part locking will
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# be much smaller
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if connection.adapter_name == 'PostgreSQL'
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execute(<<-CODE)
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CREATE FUNCTION half_md5_as_bigint(strand varchar) RETURNS bigint AS $$
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DECLARE
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strand_md5 bytea;
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BEGIN
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strand_md5 := decode(md5(strand), 'hex');
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RETURN (CAST(get_byte(strand_md5, 0) AS bigint) << 56) +
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(CAST(get_byte(strand_md5, 1) AS bigint) << 48) +
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(CAST(get_byte(strand_md5, 2) AS bigint) << 40) +
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(CAST(get_byte(strand_md5, 3) AS bigint) << 32) +
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(CAST(get_byte(strand_md5, 4) AS bigint) << 24) +
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(get_byte(strand_md5, 5) << 16) +
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(get_byte(strand_md5, 6) << 8) +
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get_byte(strand_md5, 7);
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION delayed_jobs_before_insert_row_tr_fn () RETURNS trigger AS $$
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BEGIN
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PERFORM pg_advisory_xact_lock(half_md5_as_bigint(NEW.strand));
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IF (SELECT 1 FROM delayed_jobs WHERE strand = NEW.strand LIMIT 1) = 1 THEN
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NEW.next_in_strand := 'f';
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END IF;
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RETURN NEW;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION delayed_jobs_after_delete_row_tr_fn () RETURNS trigger AS $$
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BEGIN
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PERFORM pg_advisory_xact_lock(half_md5_as_bigint(OLD.strand));
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UPDATE delayed_jobs SET next_in_strand = 't' WHERE id = (SELECT id FROM delayed_jobs j2 WHERE j2.strand = OLD.strand ORDER BY j2.strand, j2.id ASC LIMIT 1 FOR UPDATE);
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RETURN OLD;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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end
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end
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def self.down
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if connection.adapter_name == 'PostgreSQL'
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION delayed_jobs_before_insert_row_tr_fn () RETURNS trigger AS $$
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BEGIN
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LOCK delayed_jobs IN SHARE ROW EXCLUSIVE MODE;
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IF (SELECT 1 FROM delayed_jobs WHERE strand = NEW.strand LIMIT 1) = 1 THEN
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NEW.next_in_strand := 'f';
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END IF;
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RETURN NEW;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION delayed_jobs_after_delete_row_tr_fn () RETURNS trigger AS $$
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BEGIN
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UPDATE delayed_jobs SET next_in_strand = 't' WHERE id = (SELECT id FROM delayed_jobs j2 WHERE j2.strand = OLD.strand ORDER BY j2.strand, j2.id ASC LIMIT 1 FOR UPDATE);
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RETURN OLD;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute('DROP FUNCTION half_md5_as_bigint(varchar)')
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end
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end
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end
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