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Mutability (historic)
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
For historic reasons, the DSL API mixes mutable and immutable behaviour with respect to the internal representation of the QueryPart being constructed. While creating conditional expressions, column expressions (such as functions) assumes immutable behaviour, creating SQL statements does not. In other words, the following can be said:
// Conditional expressions (immutable)
// -----------------------------------
Condition a = BOOK.TITLE.eq("1984");
Condition b = BOOK.TITLE.eq("Animal Farm");
// The following can be said
a != a.or(b); // or() does not modify a
a.or(b) != a.or(b); // or() always creates new objects
// Statements (mutable)
// --------------------
SelectFromStep<?> s1 = select();
SelectJoinStep<?> s2 = s1.from(BOOK);
SelectJoinStep<?> s3 = s1.from(AUTHOR);
// The following can be said
s1 == s2; // The internal object is always the same
s2 == s3; // The internal object is always the same
On the other hand, beware that you can always extract and modify bind values from any QueryPart.
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