Joseph Doherty
49 lines
2.2 KiB
C#
49 lines
2.2 KiB
C#
namespace ScadaLink.Commons.Interfaces;
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/// <summary>
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/// Abstraction over the central AuditLog partition-function roll-forward
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/// operation. M6-T5 introduces a daily-cadence hosted service
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/// (<c>AuditLogPartitionMaintenanceService</c>) that calls
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/// <see cref="EnsureLookaheadAsync"/> to make sure
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/// <c>pf_AuditLog_Month</c> always has at least <c>LookaheadMonths</c> of
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/// future boundaries available — otherwise inserts past the highest
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/// boundary land in a single ever-growing tail partition that
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/// <c>SwitchOutPartitionAsync</c> cannot purge cleanly.
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/// </summary>
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/// <remarks>
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/// <para>
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/// The interface lives in <c>ScadaLink.Commons</c> so the central hosted
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/// service in <c>ScadaLink.AuditLog</c> can depend on it without taking a
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/// reference on <c>ScadaLink.ConfigurationDatabase</c>; the EF-based
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/// implementation ships in
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/// <c>ScadaLink.ConfigurationDatabase.Maintenance.AuditLogPartitionMaintenance</c>
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/// and is registered by <c>AddConfigurationDatabase</c>.
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/// </para>
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/// <para>
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/// Both methods read <c>sys.partition_range_values</c> / mutate
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/// <c>pf_AuditLog_Month</c> via raw SQL — there is no EF model for a
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/// partition function. The interface deliberately exposes only the two
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/// operations the hosted service needs; it is not a general partition-DDL
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/// surface.
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/// </para>
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/// </remarks>
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public interface IPartitionMaintenance
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{
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/// <summary>
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/// Splits new monthly boundaries on <c>pf_AuditLog_Month</c> so the
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/// function covers at least <paramref name="lookaheadMonths"/> future
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/// months relative to <see cref="DateTime.UtcNow"/>. Idempotent — a
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/// boundary that already exists is skipped rather than re-issued.
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/// Returns the boundaries actually added, in chronological order.
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/// </summary>
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Task<IReadOnlyList<DateTime>> EnsureLookaheadAsync(int lookaheadMonths, CancellationToken ct = default);
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/// <summary>
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/// Reads the current maximum boundary value from
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/// <c>sys.partition_range_values</c> for <c>pf_AuditLog_Month</c>.
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/// Returns <c>null</c> when the partition function does not exist or
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/// has no boundaries.
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/// </summary>
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Task<DateTime?> GetMaxBoundaryAsync(CancellationToken ct = default);
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}
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