Henry
26bf26fc20
Co-authored-by: nova28 <17953305+nova28@users.noreply.github.com> Co-authored-by: Carlos Florencio <carlosmflorencio@gmail.com>
29 lines
1.3 KiB
Go
29 lines
1.3 KiB
Go
package dialect
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import "fmt"
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// OrderedIDConcat returns the SQL fragment for a scalar subquery that
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// comma-joins the `id` column of `SELECT id FROM tasks WHERE <where>`, in
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// ascending id order. The two dialects place the ordering differently:
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// SQLite's GROUP_CONCAT has no ORDER BY of its own, so ordering comes from
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// an ORDER BY inside the subquery; PostgreSQL's string_agg takes an ORDER BY
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// inside the aggregate call itself. Writing one and assuming the other
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// matches is how the two dialects silently diverge on row order — see
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// docs/specs/office/system-design/parent-wake-wave-identity.md, "Backstop
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// admission".
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//
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// where is the WHERE clause body (no leading "WHERE", no trailing
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// "ORDER BY") of the `tasks` subquery — the caller supplies the predicate,
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// this helper only owns the aggregate/order-by placement split.
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//
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// SQLite: (SELECT GROUP_CONCAT(w.id, ',') FROM (SELECT id FROM tasks WHERE <where> ORDER BY id) w)
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// Postgres: (SELECT string_agg(w.id, ',' ORDER BY w.id) FROM (SELECT id FROM tasks WHERE <where>) w)
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func OrderedIDConcat(driver, where string) string {
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if IsPostgres(driver) {
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return fmt.Sprintf(
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"(SELECT string_agg(w.id, ',' ORDER BY w.id) FROM (SELECT id FROM tasks WHERE %s) w)", where)
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}
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return fmt.Sprintf(
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"(SELECT GROUP_CONCAT(w.id, ',') FROM (SELECT id FROM tasks WHERE %s ORDER BY id) w)", where)
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}
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