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Fix array slicing of int2vector and oidvector values.
The previous coding labeled expressions such as pg_index.indkey[1:3] as being of int2vector type; which is not right because the subscript bounds of such a result don't, in general, satisfy the restrictions of int2vector. To fix, implicitly promote the result of slicing int2vector to int2[], or oidvector to oid[]. This is similar to what we've done with domains over arrays, which is a good analogy because these types are very much like restricted domains of the corresponding regular-array types. A side-effect is that we now also forbid array-element updates on such columns, eg while "update pg_index set indkey[4] = 42" would have worked before if you were superuser (and corrupted your catalogs irretrievably, no doubt) it's now disallowed. This seems like a good thing since, again, some choices of subscripting would've led to results not satisfying the restrictions of int2vector. The case of an array-slice update was rejected before, though with a different error message than you get now. We could make these cases work in future if we added a cast from int2[] to int2vector (with a cast function checking the subscript restrictions) but it seems unlikely that there's any value in that. Per report from Ronan Dunklau. Back-patch to all supported branches because of the crash risks involved.
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@ -226,6 +226,18 @@ transformArrayType(Oid *arrayType, int32 *arrayTypmod)
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*/
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*arrayType = getBaseTypeAndTypmod(*arrayType, arrayTypmod);
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/*
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* We treat int2vector and oidvector as though they were domains over
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* int2[] and oid[]. This is needed because array slicing could create an
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* array that doesn't satisfy the dimensionality constraints of the
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* xxxvector type; so we want the result of a slice operation to be
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* considered to be of the more general type.
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*/
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if (*arrayType == INT2VECTOROID)
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*arrayType = INT2ARRAYOID;
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else if (*arrayType == OIDVECTOROID)
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*arrayType = OIDARRAYOID;
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/* Get the type tuple for the array */
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type_tuple_array = SearchSysCache1(TYPEOID, ObjectIdGetDatum(*arrayType));
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if (!HeapTupleIsValid(type_tuple_array))
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@ -263,6 +275,7 @@ transformArrayType(Oid *arrayType, int32 *arrayTypmod)
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* For both cases, if the source array is of a domain-over-array type,
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* the result is of the base array type or its element type; essentially,
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* we must fold a domain to its base type before applying subscripting.
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* (Note that int2vector and oidvector are treated as domains here.)
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*
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* pstate Parse state
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* arrayBase Already-transformed expression for the array as a whole
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