Fix incorrect zero extension of Datum in JIT tuple deform code

david-rowley · david-rowley · commit b8ecfbe5af4f · 2025-10-23T13:13:44.000+13:00
When JIT deformed tuples (controlled via the jit_tuple_deforming GUC), types narrower than sizeof(Datum) would be zero-extended up to Datum width. This wasn't the same as what fetch_att() does in the standard tuple deforming code. Logically the values are the same when fetching via the DatumGet*() marcos, but negative numbers are not the same in binary form. In the report, the problem was manifesting itself with: ERROR: could not find memoization table entry in a query which had a "Cache Mode: binary" Memoize node. However, it's currently unclear what else is affected. Anything that uses datum_image_eq() or datum_image_hash() on a Datum from a tuple deformed by JIT could be affected, but it may not be limited to that. The fix for this is simple: use signed extension instead of zero extension. Many thanks to Emmanuel Touzery for reporting this issue and providing steps and backup which allowed the problem to easily be recreated. Reported-by: Emmanuel Touzery <emmanuel.touzery@plandela.si> Author: David Rowley <dgrowleyml@gmail.com> Discussion: https://postgr.es/m/DB8P194MB08532256D5BAF894F241C06393F3A@DB8P194MB0853.EURP194.PROD.OUTLOOK.COM Backpatch-through: 13
diff --git a/src/backend/jit/llvm/llvmjit_deform.c b/src/backend/jit/llvm/llvmjit_deform.c
@@ -677,7 +677,7 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc,
 			v_tmp_loaddata =
 				LLVMBuildPointerCast(b, v_attdatap, vartypep, "");
 			v_tmp_loaddata = l_load(b, vartype, v_tmp_loaddata, "attr_byval");
-			v_tmp_loaddata = LLVMBuildZExt(b, v_tmp_loaddata, TypeSizeT, "");
+			v_tmp_loaddata = LLVMBuildSExt(b, v_tmp_loaddata, TypeSizeT, "");
 
 			LLVMBuildStore(b, v_tmp_loaddata, v_resultp);
 		}

Original file line number	Diff line number	Diff line change
`@@ -677,7 +677,7 @@ slot_compile_deform(LLVMJitContext *context, TupleDesc desc,`
`677`	`677`	`v_tmp_loaddata =`
`678`	`678`	`LLVMBuildPointerCast(b, v_attdatap, vartypep, "");`
`679`	`679`	`v_tmp_loaddata = l_load(b, vartype, v_tmp_loaddata, "attr_byval");`
`680`		`- v_tmp_loaddata = LLVMBuildZExt(b, v_tmp_loaddata, TypeSizeT, "");`
	`680`	`+ v_tmp_loaddata = LLVMBuildSExt(b, v_tmp_loaddata, TypeSizeT, "");`
`681`	`681`
`682`	`682`	`LLVMBuildStore(b, v_tmp_loaddata, v_resultp);`
`683`	`683`	`}`