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From: jian he <[email protected]>
To: Andres Freund <[email protected]>
Cc: Amit Langote <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Andrew Dunstan <[email protected]>
Cc: Erik Rijkers <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: remaining sql/json patches
Date: Thu, 23 Nov 2023 18:46:51 +0800
Message-ID: <CACJufxFSPropdCGkWwwD24kzMYVdwrdJueyfpMPtpCLj-7FwJQ@mail.gmail.com> (raw)
In-Reply-To: <CACJufxG4BRsg_MiDeQrneq2E79x_uUEbTQFKh7STYWm0=2pWnQ@mail.gmail.com>
References: <CA+HiwqFJQdBQzTbSt6=S_3mmYf_pb2YoRNrhL1R0zzFz5Yja=w@mail.gmail.com>
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	<CA+HiwqETtgH0ESDEEGDwTmazmtNeR7UsJS=BOoa=ghdYMo+Ufg@mail.gmail.com>
	<[email protected]>
	<CA+HiwqG_XFksg7HN_gbmcOQU00Q5bvTKeLSZ3NftewdBRw4fKA@mail.gmail.com>
	<[email protected]>
	<CA+HiwqH12dbfVdE=LgBMgt0yZBfRFcGWo7+ZiCZO-nzNjwiaxQ@mail.gmail.com>
	<[email protected]>
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	<CACJufxG4BRsg_MiDeQrneq2E79x_uUEbTQFKh7STYWm0=2pWnQ@mail.gmail.com>

+/*
+ * Evaluate or return the step address to evaluate a coercion of a JSON item
+ * to the target type.  The former if the coercion must be done right away by
+ * calling the target type's input function, and for some types, by calling
+ * json_populate_type().
+ *
+ * Returns the step address to be performed next.
+ */
+void
+ExecEvalJsonCoercionViaPopulateOrIO(ExprState *state, ExprEvalStep *op,
+ ExprContext *econtext)

the comment seems not right? it does return anything. it did the evaluation.

some logic in ExecEvalJsonCoercionViaPopulateOrIO, like if
(SOFT_ERROR_OCCURRED(escontext_p)) and if
(!InputFunctionCallSafe){...}, seems validated twice,
ExecEvalJsonCoercionFinish also did it. I uncommented the following
part, and still passed the test.
/src/backend/executor/execExprInterp.c
4452: // if (SOFT_ERROR_OCCURRED(escontext_p))
4453: // {
4454: // post_eval->error.value = BoolGetDatum(true);
4455: // *op->resvalue = (Datum) 0;
4456: // *op->resnull = true;
4457: // }

4470: // post_eval->error.value = BoolGetDatum(true);
4471: // *op->resnull = true;
4472: // *op->resvalue = (Datum) 0;
4473: return;

Correct me if I'm wrong.
like in "empty array on empty empty object on error", the "empty
array" refers to constant literal '[]' the assumed data type is jsonb,
the "empty object" refers to const literal '{}', the assumed data type
is jsonb.

--these two queries will fail very early, before ExecEvalJsonExprPath.
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.a' RETURNING int4range
default '[1.1,2]' on error);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.a' RETURNING int4range
default '[1.1,2]' on empty);

-----these four will fail later, and will call
ExecEvalJsonCoercionViaPopulateOrIO twice.
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
object on empty empty object on error);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
array on empty empty array on error);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
array on empty empty object on error);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
object on empty empty array on error);

-----however these four will not fail.
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
object on error);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
array on error);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
array on empty);
SELECT JSON_QUERY(jsonb '{"a":[3,4]}', '$.z' RETURNING int4range empty
object on empty);

should the last four query fail or just return null?

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