spring-projects/spring-ai · error · IllegalStateException

The 'IN' operator should have been transformed into chain…

Error message

The 'IN' operator should have been transformed into chain of OR/EQ expressions.

What it means

The Weaviate converter cannot emit IN directly: before conversion, IN expressions are (or must be) transformed into a chain of OR/EQ expressions, because Weaviate's GraphQL where filter has no native IN operator. Encountering IN in getOperationSymbol means the pre-transformation step didn't run, so an IllegalStateException is thrown.

Solutions

Let the standard conversion path (convert/doExpression) handle the expression — it expands IN into OR of EQ automatically.
Manually rewrite your filter as OR of EQ expressions: (a==1 OR a==2 OR a==3).
If you override doExpression in a subclass, ensure you still expand IN/NIN before delegating to getOperationSymbol.

Example fix

// before
var expr = new Filter.Expression(IN, new Key("color"), new Value(List.of("red", "blue"))); // passed straight to operand conversion
// after
var or1 = new Filter.Expression(EQ, new Key("color"), new Value("red"));
var or2 = new Filter.Expression(EQ, new Key("color"), new Value("blue"));
var expr = new Filter.Expression(OR, or1, or2);

Defensive patterns

Strategy: type-guard

Validate before calling

if (expr.type() == Filter.ExpressionType.IN) { throw new IllegalArgumentException("Use OR/EQ chains or the standard conversion path for IN"); }

Type guard

static boolean requiresExpansion(Filter.Expression e) { return e.type() == Filter.ExpressionType.IN || e.type() == Filter.ExpressionType.NIN; }

Try / catch

try { String q = converter.convertExpression(expr); } catch (IllegalStateException e) { if (e.getMessage().contains("'IN' operator")) { /* expand IN into OR/EQ yourself */ } else throw e; }

Prevention

Always convert through the full converter pipeline, never call getOperationSymbol directly
Express set membership with IN and let the converter expand it
Avoid subclass overrides that skip the IN expansion step

When it happens

Trigger: Calling the converter with a Filter.Expression of type IN that bypassed the standard doExpression transformation, e.g. invoking getOperationSymbol directly or a code path that skips the IN-expansion preprocessing.

Common situations: Custom code calling the converter internals directly; a subclass overriding doExpression and removing the IN expansion; version mismatch where the transformation was expected upstream.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of spring-projects/spring-ai@98a7beda4f (2026-09-11). Data as JSON: /api/errors/824809862cd158be. Report an issue: GitHub.

Appendix: source

Thrown at vector-stores/spring-ai-weaviate-store/src/main/java/org/springframework/ai/vectorstore/weaviate/WeaviateFilterExpressionConverter.java:118

		}
		else {
			this.convertOperand(exp.left(), context);
			context.append(getOperationSymbol(exp));
			this.convertOperand(exp.right(), context);
		}
	}

	private String getOperationSymbol(Expression exp) {
		return switch (exp.type()) {
			case AND -> "operator:And \n";
			case OR -> "operator:Or \n";
			case EQ -> "operator:Equal \n";
			case NE -> "operator:NotEqual \n";
			case LT -> "operator:LessThan \n";
			case LTE -> "operator:LessThanEqual \n";
			case GT -> "operator:GreaterThan \n";
			case GTE -> "operator:GreaterThanEqual \n";
			case IN -> throw new IllegalStateException(
					"The 'IN' operator should have been transformed into chain of OR/EQ expressions.");
			case NIN -> throw new IllegalStateException(
					"The 'NIN' operator should have been transformed into chain of AND/NEQ expressions.");
			default -> throw new UnsupportedOperationException("Not supported expression type:" + exp.type());
		};
	}

	@Override
	protected void doKey(Key key, StringBuilder context) {
		var identifier = (hasOuterQuotes(key.key())) ? removeOuterQuotes(key.key()) : key.key();
		context.append("path:[");
		emitJsonValue(withMetaPrefix(identifier), context);
		context.append("] \n");
	}

	public String withMetaPrefix(String identifier) {
		if (SYSTEM_IDENTIFIERS.contains(identifier)) {
			return identifier;

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