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State dependencies between two or model - design / retrieval technique
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| def self.filter_by_job_status(job_status) | |
| projects = where(nil) | |
| if job_status == :completed | |
| match_all = <<~EOD | |
| EXISTS ( SELECT 1 FROM jobs WHERE jobs.project_id = projects.id ) AND | |
| NOT EXISTS ( SELECT 1 from jobs WHERE jobs.project_id = projects.id AND jobs.status NOT IN (?) ) | |
| EOD | |
| return projects.where([match_all, job_status]) | |
| end | |
| projects.where(['EXISTS ( SELECT 1 FROM jobs WHERE jobs.project_id = projects.id AND jobs.status = ? )', job_status]) | |
| end |
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This problem happens a lot for example in Spree commerce order state and shipment state depend on each other.
When an order is first created, the order sets status to shipments. when the shipment state changes to ship, the order should be aware of all shipment states are shipped then the order state should be shipped.
Spree also stores shipment_state as a calculated field to avoid joining with the shipments table.