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Fix delta external table schema diff, script syntax, and cleanup #164

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Merged
ashleyvansp merged 3 commits into from
Apr 13, 2026
+26 −3
Merged

Fix delta external table schema diff, script syntax, and cleanup #164

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11431ac
Fix delta external table schema diff, script syntax, and cleanup
ashleyvansp Apr 10, 2026
5d626bb
Merge branch 'main' into fix/delta-schema-perpetual-diff
ashleyvansp Apr 13, 2026
c2e88ac
Address comments
ashleyvansp Apr 13, 2026
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15 changes: 15 additions & 0 deletions KustoSchemaTools/Changes/DatabaseChanges.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,21 @@ public static List<IChange> GenerateChanges(Database oldState, Database newState
result.AddRange(mvChanges);
result.AddRange(GenerateScriptCompareChanges(oldState, newState, db => db.ContinuousExports, nameof(newState.ContinuousExports), log));
result.AddRange(GenerateScriptCompareChanges(oldState, newState, db => db.Functions, nameof(newState.Functions), log));

// For delta external tables, the schema is auto-inferred from the delta log.
// If the YAML doesn't specify a schema, clear the cluster-side schema so it
// doesn't cause a perpetual diff. If the YAML does specify a schema, keep the
// cluster-side schema for proper comparison.
foreach (var et in newState.ExternalTables)
{
if (et.Value.Kind?.ToLower() == "delta"
&& et.Value.Schema?.Any() != true
&& oldState.ExternalTables.ContainsKey(et.Key))
{
oldState.ExternalTables[et.Key].Schema = null;
}
}

result.AddRange(GenerateScriptCompareChanges(oldState, newState, db => db.ExternalTables, nameof(newState.ExternalTables), log));

if (newState.EntityGroups.Any())
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13 changes: 9 additions & 4 deletions KustoSchemaTools/Model/ExternalTable.cs
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Expand Up @@ -137,20 +137,25 @@ private string CreateSqlScript(string name)

private string CreateDeltaScript(string name)
{
if (string.IsNullOrWhiteSpace(DataFormat)) throw new ArgumentException("DataFormat can't be empty");

var sb = new StringBuilder();
sb.AppendLine($".create-or-alter external table {name}");
if (Schema?.Any() == true)
{
sb.AppendLine($"({string.Join(", ", Schema.Select(c => $"{c.Key.BracketIfIdentifier()}:{c.Value}"))})");
}
sb.AppendLine("kind=delta");
sb.AppendLine($"(h@'{ConnectionString}'");
sb.AppendLine($"(h@'{ConnectionString}')");

var withProps = new List<string>();
if (!string.IsNullOrEmpty(Folder)) withProps.Add($"folder='{Folder}'");
if (!string.IsNullOrEmpty(DocString)) withProps.Add($"docString='{DocString}'");
var ext = string.IsNullOrWhiteSpace(FileExtensions) ? "" : FileExtensions.StartsWith(".") ? FileExtensions : "." + FileExtensions;
if (!string.IsNullOrEmpty(ext)) withProps.Add($"fileExtension='{ext}'");

sb.AppendLine($"with(folder='{Folder}', docString='{DocString}', fileExtension='{ext}') ");
if (withProps.Any())
{
sb.AppendLine($"with({string.Join(", ", withProps)})");
}

return sb.ToString();
}
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