Fix double detoasting of compressed jsonbs

Author: Nikita Glukhov

src/backend/utils/adt/jsonb_util.c

@@ -2850,15 +2850,13 @@ jsonbzIteratorInit(JsonContainer *jc)
 }
 
 static void
-jsonbzInit(JsonContainerData *jc, Datum value)
+jsonbzInitFromCompresedDatum(JsonContainerData *jc, CompressedDatum *cd)
 {
 	CompressedJsonb *cjb = palloc(sizeof(*cjb));
-	CompressedDatum *cd = palloc(sizeof(*cd));
 
 	cjb->datum = cd;
 	cjb->offset = offsetof(Jsonb, root);
 
-	CompressedDatumInit(cd, value);
 	if (!jsonb_partial_decompression)
 		CompressedDatumDecompressAll(cd);
 	else
@@ -2867,6 +2865,16 @@ jsonbzInit(JsonContainerData *jc, Datum value)
 	jsonbzInitContainer(jc, cjb, VARSIZE_ANY_EXHDR(cd->data)); // cd->total_len - VARHDRSZ
 }
 
+static void
+jsonbzInit(JsonContainerData *jc, Datum value)
+{
+	CompressedDatum *cd = palloc(sizeof(*cd));
+
+	CompressedDatumInit(cd, value);
+
+	jsonbzInitFromCompresedDatum(jc, cd);
+}
+
 JsonContainerOps
 jsonbzContainerOps =
 {
@@ -2910,7 +2918,8 @@ DatumGetJsonbPC(Datum datum, Json *tmp, bool copy)
 
 	js = JsonExpand(tmp, (Datum) 0, false, &jsonbzContainerOps);
 
-	jsonbzInit(&js->root, datum);
+	jsonbzInitFromCompresedDatum(&js->root,
+								 memcpy(palloc(sizeof(cd)), &cd, sizeof(cd)));
 
 	return js;
 }