Add v2 file contract revisions

[chris124567]

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[peterjan]

LGTM, left some nits and suggestions on fillV2TransactionFileContractRevisions

[peterjan]

Is this panic absolutely necessary? I can see how we want to, in some cases, panic when we have db corruption but seems quite harsh.

[peterjan]

I think the statements can be combined using UNION ALL, you add something like "SELECT "parent", ... UNION ALL SELECT "revision" to differentiate the two and then collectFileContracts returns two slices.

var kind string
if err := rows.Scan(&kind); err != nil {
    return nil, fmt.Errorf("failed to scan contract type: %w", err)
}

fce, err := scanV2FileContract(rows)
if err != nil {
    return nil, fmt.Errorf("failed to scan file contract: %w", err)
}

if kind == "parent" {
    parents = append(contracts, fce)
} else {
    revisions = append(contracts, fce)
}

[peterjan]

Not sure how well this would perform but something this would get rid of the duplicate select expression and clearly show what's happening.

WITH 
    base_data AS (SELECT field1, field2, field3 FROM t1 INNER JOIN t2),
    revision_data AS (SELECT *, "revision" as kind FROM base_data),
    parent_data AS (SELECT *, "parent" as kind FROM base_data)
SELECT * FROM revision_data ORDER BY x
UNION ALL
SELECT * FROM parent_data ORDER BY x

[chris124567]

Tried doing something along these lines but I don't think this is worth it unless we find we're having performance issues with the current queries. It makes the query more complicated and it seems that calling Scan twice on the same Rows doesn't work so we'd need to change the FCE scan helper too because we can't get the kind separately from the rest of the data.