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SQL/JSON: Always coerce JsonExpr result at runtime

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Instead of looking up casts at parse time for converting the result
of JsonPath* query functions to the specified or the default
RETURNING type, always perform the conversion at runtime using either
the target type's input function or the function
json_populate_type().

There are two motivations for this change:

1. json_populate_type() coerces to types with typmod such that any
   string values that exceed length limit cause an error instead of
   silent truncation, which is necessary to be standard-conforming.

2. It was possible to end up with a cast expression that doesn't
   support soft handling of errors causing bugs in the of handling
   ON ERROR clause.

JsonExpr.coercion_expr which would store the cast expression is no
longer necessary, so remove.

Bump catversion because stored rules change because of the above
removal.

Reported-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion: Discussion: https://postgr.es/m/202405271326.5a5rprki64aw%40alvherre.pgsql
This commit is contained in:
Amit Langote
2024-06-28 21:58:13 +09:00
parent c2d93c3802
commit 716bd12d22
15 changed files with 213 additions and 309 deletions
Download Patch File Download Diff File Expand all files Collapse all files

52
src/backend/executor/execExpr.c
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@@ -92,7 +92,7 @@ static void ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
Datum *resv, bool *resnull,
ExprEvalStep *scratch);
static void ExecInitJsonCoercion(ExprState *state, JsonReturning *returning,
ErrorSaveContext *escontext,
ErrorSaveContext *escontext, bool omit_quotes,
Datum *resv, bool *resnull);
@@ -4313,13 +4313,15 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
ExprEvalPushStep(state, scratch);
/*
* Jump to coerce the NULL using coercion_expr if present. Coercing NULL
* is only interesting when the RETURNING type is a domain whose
* constraints must be checked. jsexpr->coercion_expr containing a
* CoerceToDomain node must have been set in that case.
* Jump to coerce the NULL using json_populate_type() if needed. Coercing
* NULL is only interesting when the RETURNING type is a domain whose
* constraints must be checked. jsexpr->use_json_coercion must have been
* set in that case.
*/
if (jsexpr->coercion_expr)
if (get_typtype(jsexpr->returning->typid) == TYPTYPE_DOMAIN &&
DomainHasConstraints(jsexpr->returning->typid))
{
Assert(jsexpr->use_json_coercion);
scratch->opcode = EEOP_JUMP;
scratch->d.jump.jumpdone = state->steps_len + 1;
ExprEvalPushStep(state, scratch);
@@ -4337,33 +4339,12 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
* NULL returned on NULL input as described above.
*/
jsestate->jump_eval_coercion = -1;
if (jsexpr->coercion_expr)
{
Datum *save_innermost_caseval;
bool *save_innermost_casenull;
ErrorSaveContext *save_escontext;
jsestate->jump_eval_coercion = state->steps_len;
save_innermost_caseval = state->innermost_caseval;
save_innermost_casenull = state->innermost_casenull;
save_escontext = state->escontext;
state->innermost_caseval = resv;
state->innermost_casenull = resnull;
state->escontext = escontext;
ExecInitExprRec((Expr *) jsexpr->coercion_expr, state, resv, resnull);
state->innermost_caseval = save_innermost_caseval;
state->innermost_casenull = save_innermost_casenull;
state->escontext = save_escontext;
}
else if (jsexpr->use_json_coercion)
if (jsexpr->use_json_coercion)
{
jsestate->jump_eval_coercion = state->steps_len;
ExecInitJsonCoercion(state, jsexpr->returning, escontext, resv, resnull);
ExecInitJsonCoercion(state, jsexpr->returning, escontext,
jsexpr->omit_quotes, resv, resnull);
}
else if (jsexpr->use_io_coercion)
{
@@ -4435,8 +4416,8 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
/* Step to coerce the ON ERROR expression if needed */
if (jsexpr->on_error->coerce)
ExecInitJsonCoercion(state, jsexpr->returning, escontext, resv,
resnull);
ExecInitJsonCoercion(state, jsexpr->returning, escontext,
jsexpr->omit_quotes, resv, resnull);
/* JUMP to end to skip the ON EMPTY steps added below. */
jumps_to_end = lappend_int(jumps_to_end, state->steps_len);
@@ -4468,8 +4449,8 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
/* Step to coerce the ON EMPTY expression if needed */
if (jsexpr->on_empty->coerce)
ExecInitJsonCoercion(state, jsexpr->returning, escontext, resv,
resnull);
ExecInitJsonCoercion(state, jsexpr->returning, escontext,
jsexpr->omit_quotes, resv, resnull);
}
foreach(lc, jumps_to_end)
@@ -4488,7 +4469,7 @@ ExecInitJsonExpr(JsonExpr *jsexpr, ExprState *state,
*/
static void
ExecInitJsonCoercion(ExprState *state, JsonReturning *returning,
ErrorSaveContext *escontext,
ErrorSaveContext *escontext, bool omit_quotes,
Datum *resv, bool *resnull)
{
ExprEvalStep scratch = {0};
@@ -4501,5 +4482,6 @@ ExecInitJsonCoercion(ExprState *state, JsonReturning *returning,
scratch.d.jsonexpr_coercion.targettypmod = returning->typmod;
scratch.d.jsonexpr_coercion.json_populate_type_cache = NULL;
scratch.d.jsonexpr_coercion.escontext = escontext;
scratch.d.jsonexpr_coercion.omit_quotes = omit_quotes;
ExprEvalPushStep(state, &scratch);
}