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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

51
src/backend/executor/execExprInterp.c
View File

@ -4303,8 +4303,14 @@ ExecEvalJsonExprPath(ExprState *state, ExprEvalStep *op,
if (!error)
{
*op->resvalue = BoolGetDatum(exists);
*op->resnull = false;
if (jsexpr->use_json_coercion)
*op->resvalue = DirectFunctionCall1(jsonb_in,
BoolGetDatum(exists) ?
CStringGetDatum("true") :
CStringGetDatum("false"));
else
*op->resvalue = BoolGetDatum(exists);
}
}
break;
@ -4316,22 +4322,6 @@ ExecEvalJsonExprPath(ExprState *state, ExprEvalStep *op,
jsexpr->column_name);
*op->resnull = (DatumGetPointer(*op->resvalue) == NULL);
/* Handle OMIT QUOTES. */
if (!*op->resnull && jsexpr->omit_quotes)
{
val_string = JsonbUnquote(DatumGetJsonbP(*op->resvalue));
/*
* Pass the string as a text value to the cast expression if
* one present. If not, use the input function call below to
* do the coercion.
*/
if (jump_eval_coercion >= 0)
*op->resvalue =
DirectFunctionCall1(textin,
PointerGetDatum(val_string));
}
break;
case JSON_VALUE_OP:
@ -4343,7 +4333,7 @@ ExecEvalJsonExprPath(ExprState *state, ExprEvalStep *op,
if (jbv == NULL)
{
/* Will be coerced with coercion_expr, if any. */
/* Will be coerced with json_populate_type(), if needed. */
*op->resvalue = (Datum) 0;
*op->resnull = true;
}
@ -4355,18 +4345,22 @@ ExecEvalJsonExprPath(ExprState *state, ExprEvalStep *op,
val_string = DatumGetCString(DirectFunctionCall1(jsonb_out,
JsonbPGetDatum(JsonbValueToJsonb(jbv))));
}
else if (jsexpr->use_json_coercion)
{
*op->resvalue = JsonbPGetDatum(JsonbValueToJsonb(jbv));
*op->resnull = false;
}
else
{
val_string = ExecGetJsonValueItemString(jbv, op->resnull);
/*
* Pass the string as a text value to the cast
* expression if one present. If not, use the input
* function call below to do the coercion.
* Simply convert to the default RETURNING type (text)
* if no coercion needed.
*/
*op->resvalue = PointerGetDatum(val_string);
if (jump_eval_coercion >= 0)
*op->resvalue = DirectFunctionCall1(textin, *op->resvalue);
if (!jsexpr->use_io_coercion)
*op->resvalue = DirectFunctionCall1(textin,
CStringGetDatum(val_string));
}
}
break;
@ -4545,13 +4539,14 @@ ExecEvalJsonCoercion(ExprState *state, ExprEvalStep *op,
op->d.jsonexpr_coercion.targettypmod,
&op->d.jsonexpr_coercion.json_populate_type_cache,
econtext->ecxt_per_query_memory,
op->resnull, (Node *) escontext);
op->resnull,
op->d.jsonexpr_coercion.omit_quotes,
(Node *) escontext);
}
/*
* Checks if an error occurred either when evaluating JsonExpr.coercion_expr or
* in ExecEvalJsonCoercion(). If so, this sets JsonExprState.error to trigger
* the ON ERROR handling steps.
* Checks if an error occurred in ExecEvalJsonCoercion(). If so, this sets
* JsonExprState.error to trigger the ON ERROR handling steps.
*/
void
ExecEvalJsonCoercionFinish(ExprState *state, ExprEvalStep *op)