Avoid some pnstrdup()s when constructing jsonb

This speeds up text to jsonb parsing and hstore to jsonb conversions
somewhat.

contrib/hstore/hstore_io.c

@@ -1386,7 +1386,7 @@ hstore_to_jsonb(PG_FUNCTION_ARGS)
 
 		key.type = jbvString;
 		key.val.string.len = HS_KEYLEN(entries, i);
-		key.val.string.val = pnstrdup(HS_KEY(entries, base, i), key.val.string.len);
+		key.val.string.val = HS_KEY(entries, base, i);
 
 		res = pushJsonbValue(&state, WJB_KEY, &key);
 
@@ -1398,7 +1398,7 @@ hstore_to_jsonb(PG_FUNCTION_ARGS)
 		{
 			val.type = jbvString;
 			val.val.string.len = HS_VALLEN(entries, i);
-			val.val.string.val = pnstrdup(HS_VAL(entries, base, i), val.val.string.len);
+			val.val.string.val = HS_VAL(entries, base, i);
 		}
 		res = pushJsonbValue(&state, WJB_VALUE, &val);
 	}
@@ -1433,7 +1433,7 @@ hstore_to_jsonb_loose(PG_FUNCTION_ARGS)
 
 		key.type = jbvString;
 		key.val.string.len = HS_KEYLEN(entries, i);
-		key.val.string.val = pnstrdup(HS_KEY(entries, base, i), key.val.string.len);
+		key.val.string.val = HS_KEY(entries, base, i);
 
 		res = pushJsonbValue(&state, WJB_KEY, &key);
 
@@ -1507,7 +1507,7 @@ hstore_to_jsonb_loose(PG_FUNCTION_ARGS)
 			{
 				val.type = jbvString;
 				val.val.string.len = HS_VALLEN(entries, i);
-				val.val.string.val = pnstrdup(HS_VAL(entries, base, i), val.val.string.len);
+				val.val.string.val = HS_VAL(entries, base, i);
 			}
 		}
 		res = pushJsonbValue(&state, WJB_VALUE, &val);

src/backend/utils/adt/json.c

@@ -381,9 +381,6 @@ parse_object_field(JsonLexContext *lex, JsonSemAction *sem)
 
 	if (oend != NULL)
 		(*oend) (sem->semstate, fname, isnull);
-
-	if (fname != NULL)
-		pfree(fname);
 }
 
 static void

src/backend/utils/adt/jsonb.c

@@ -247,7 +247,7 @@ jsonb_in_object_field_start(void *pstate, char *fname, bool isnull)
 	Assert(fname != NULL);
 	v.type = jbvString;
 	v.val.string.len = checkStringLen(strlen(fname));
-	v.val.string.val = pnstrdup(fname, v.val.string.len);
+	v.val.string.val = fname;
 
 	_state->res = pushJsonbValue(&_state->parseState, WJB_KEY, &v);
 }
@@ -295,7 +295,7 @@ jsonb_in_scalar(void *pstate, char *token, JsonTokenType tokentype)
 			Assert(token != NULL);
 			v.type = jbvString;
 			v.val.string.len = checkStringLen(strlen(token));
-			v.val.string.val = pnstrdup(token, v.val.string.len);
+			v.val.string.val = token;
 			break;
 		case JSON_TOKEN_NUMBER:
 

src/include/utils/jsonapi.h

@@ -73,6 +73,10 @@ typedef void (*json_scalar_action) (void *state, char *token, JsonTokenType toke
  * point, Likewise, semstate can be NULL. Using an all-NULL structure amounts
  * to doing a pure parse with no side-effects, and is therefore exactly
  * what the json input routines do.
+ *
+ * The 'fname' and 'token' strings passed to these actions are palloc'd.
+ * They are not free'd or used further by the parser, so the action function
+ * is free to do what it wishes with them.
  */
 typedef struct JsonSemAction
 {