Hi Nikita, On Wed, Aug 24, 2022 at 6:29 AM Nikita Glukhov <n.glu...@postgrespro.ru> wrote: > Here is my plan: > > 0. Take my last v7-0001 patch as a base. It already contains refactoring > of JsonCoercion code. (Fix 0002 is not needed anymore, because it is for > json[b] domains, which simply will not be supported.) > > 1. Replace JSON_COERCION_VIA_EXPR in JsonCoercion with new > JsonCoercionType(s) for hardcoded coercions. > > 2. Disable all non-JSON-compatible output types in coerceJsonFuncExpr(). > > 3. Add missing safe type input functions for integers, numerics, and > maybe others. > > 4. Implement hardcoded coercions using these functions in > ExecEvalJsonExprCoercion(). > > 5. Try to allow only constants (and also maybe column/parameter > references) in JSON_VALUE's DEFAULT expressions. This should be enough > for the most of practical cases. JSON_QUERY even does not have DEFAULT > expressions -- it has only EMPTY ARRAY and EMPTY OBJECT, which can be > treated as simple JSON constants. > > But it is possible to allow all other expressions in ERROR ON ERROR > case, and I don't know if it will be consistent enough to allow some > expressions in one case and deny in other. > > And there is another problem: expressions can be only checked for > Const-ness only after expression simplification. AFAIU, at the > parsing stage they look like 'string'::type. So, it's unclear if it > is correct to check expressions in ExecInitExpr().
IIUC, the idea is to remove the support for `DEFAULT expression` in the following, no? json_value ( context_item, path_expression ... [ { ERROR | NULL | DEFAULT expression } ON EMPTY ] [ { ERROR | NULL | DEFAULT expression } ON ERROR ]) json_query ( context_item, path_expression ... [ { ERROR | NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression } ON EMPTY ] [ { ERROR | NULL | EMPTY { [ ARRAY ] | OBJECT } | DEFAULT expression } ON ERROR ]) If that's the case, I'd imagine that `default_expr` in the following will be NULL for now: /* * JsonBehavior - * representation of JSON ON ... BEHAVIOR clause */ typedef struct JsonBehavior { NodeTag type; JsonBehaviorType btype; /* behavior type */ Node *default_expr; /* default expression, if any */ } JsonBehavior; And if so, no expression left to check the Const-ness of? -- Thanks, Amit Langote EDB: http://www.enterprisedb.com