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SQL/JSON: Fix some oversights in commit b6e1157e7

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The decision in b6e1157e7 to ignore raw_expr when evaluating a
JsonValueExpr was incorrect.  While its value is not ultimately
used (since formatted_expr's value is), failing to initialize it
can lead to problems, for instance,  when the expression tree in
raw_expr contains Aggref nodes, which must be initialized to
ensure the parent Agg node works correctly.

Also, optimize eval_const_expressions_mutator()'s handling of
JsonValueExpr a bit.  Currently, when formatted_expr cannot be folded
into a constant, we end up processing it twice -- once directly in
eval_const_expressions_mutator() and again recursively via
ece_generic_processing().  This recursive processing is required to
handle raw_expr. To avoid the redundant processing of formatted_expr,
we now  process raw_expr directly in eval_const_expressions_mutator().

Finally, update the comment of JsonValueExpr to describe the roles of
raw_expr and formatted_expr more clearly.

Bug: #18657
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Diagnosed-by: Fabio R. Sluzala <fabio3rs@gmail.com>
Diagnosed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/18657-1b90ccce2b16bdb8@postgresql.org
Backpatch-through: 16
This commit is contained in:
Amit Langote
2024-10-20 12:21:03 +09:00
parent 0f4045814f
commit fa4f11854c
5 changed files with 92 additions and 11 deletions
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14
src/include/nodes/primnodes.h
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@@ -1596,15 +1596,19 @@ typedef struct JsonReturning
* JsonValueExpr -
* representation of JSON value expression (expr [FORMAT JsonFormat])
*
* The actual value is obtained by evaluating formatted_expr. raw_expr is
* only there for displaying the original user-written expression and is not
* evaluated by ExecInterpExpr() and eval_const_exprs_mutator().
* raw_expr is the user-specified value, while formatted_expr is the value
* obtained by coercing raw_expr to the type required by either the FORMAT
* clause or an enclosing node's RETURNING clause.
*
* When deparsing a JsonValueExpr, get_rule_expr() prints raw_expr. However,
* during the evaluation of a JsonValueExpr, the value of formatted_expr
* takes precedence over that of raw_expr.
*/
typedef struct JsonValueExpr
{
NodeTag type;
Expr *raw_expr; /* raw expression */
Expr *formatted_expr; /* formatted expression */
Expr *raw_expr; /* user-specified expression */
Expr *formatted_expr; /* coerced formatted expression */
JsonFormat *format; /* FORMAT clause, if specified */
} JsonValueExpr;