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Troubleshooting

EInvalidOperation: "Sequence contains no elements"​

First, Last, Single, Min, Max, and Aggregate (without seed) raise this when the sequence is empty.

Fix: use the OrDefault variant or add Any check first:

if LQuery.Any then
  var LFirst := LQuery.First
else
  var LFirst := Default(TMyType);

// Or simply:
var LFirst := LQuery.FirstOrDefault;

EInvalidOperation: "Scalar query returned no results"​

Thrown by IColligoQueryable<T> terminal operators when the database query returns no rows.

Fix: use FirstOrDefault / LastOrDefault / SingleOrDefault instead of their non-defaulting variants.

EArgumentNilException: "Predicate cannot be nil"​

Where, TakeWhile, SkipWhile, and All raise this when the predicate parameter is not assigned.

Fix: always assign a valid anonymous function before calling.

Pipeline returns wrong results after reuse​

IColligoEnumerable<T> is a value record. If you assign it to a local variable and then modify it (chain more operators), the original variable is unchanged because records are copied by value.

var LBase := TColligoArray<Integer>.From([1, 2, 3, 4, 5]);

// LBase is not modified — LFiltered is a new record:
var LFiltered := LBase.Where(function(const X: Integer): Boolean begin Result := X > 2 end);

Linux64: "Undeclared identifier UCS4LowerCase"​

TColligoString.ToLower/ToUpper previously referenced UCS4LowerCase/UCS4UpperCase which do not exist on Linux. This is fixed in current source — the fallback uses System.SysUtils.LowerCase/UpperCase. Ensure you are on the latest main branch.

IColligoQueryable: "Provider not assigned for query building"​

TColligoQueryable<T>.BuildQuery raises this when the internal provider is nil. This can happen if you call Create(nil) directly.

Fix: always use CreateForDatabase(...) or provide a non-nil IColligoQueryableBase<T>.

IColligoQueryable: "Generated SQL is empty"​

_ExecuteScalar raises this when the FluentSQL AST generates an empty string. This usually means From(...) was not called.

Fix: ensure From('TABLE_NAME') is the first call in the chain.

IColligoQueryable methods not compiling​

IColligoQueryable<T> method bodies require {$DEFINE QUERYABLE}. Operator declarations always compile; method bodies do not without the define.

Fix: add {$DEFINE QUERYABLE} to your project's conditional defines or to a .inc file included before Colligo.Queryable.

TColligoList<T> with AOwnerships deletes objects on removal​

When AOwnerships = True and T is a class, TColligoList<T> calls .Free on each removed object. If another reference to the same object exists elsewhere, this causes a dangling pointer.

Fix: use AOwnerships = False (the default) unless you want the list to own the objects exclusively.