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From: jian he <jian.universality@gmail.com>
Date: Sun, 29 Dec 2024 00:46:28 +0800
Message-ID: 
 <CACJufxEb1prZo4G4BhYym1VqKHaPVUv3SoggTR4uCqgCRY7Q-Q@mail.gmail.com>
Subject: Re: Re: proposal: schema variables
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>,
 Laurenz Albe <laurenz.albe@cybertec.at>,
	Erik Rijkers <er@xs4all.nl>, Michael Paquier <michael@paquier.xyz>,
	Amit Kapila <amit.kapila16@gmail.com>, DUVAL REMI <REMI.DUVAL@cheops.fr>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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Precedence: bulk

hi.

+ if (stmt->collClause)
+ collation = LookupCollation(pstate,
+ stmt->collClause->collname,
+ stmt->collClause->location);
+ else
+ collation = typcollation;;

two semi-colon. should be only one.
------------------<<>>>---------------
+ /* locks the variable with an AccessShareLock */
+ varid = IdentifyVariable(names, &attrname, &not_unique, false);
+ if (not_unique)
+ ereport(ERROR,
+ (errcode(ERRCODE_AMBIGUOUS_PARAMETER),
+ errmsg("target \"%s\" of LET command is ambiguous",
+ NameListToString(names)),
+ parser_errposition(pstate, stmt->location)));

the following are tests for the above "LET command is ambiguous" error message.

create schema test;
CREATE TYPE test AS (test int);
CREATE variable test.test as test;
set search_path to test;
let test.test = 1;
------------------<<>>>---------------
+ else
+ {
+ /* the last field of list can be star too */
+ Assert(IsA(field2, A_Star));
+
+ /*
+ * In this case, the field1 should be variable name. But
+ * direct unboxing of composite session variables is not
+ * supported now, and then we don't need to try lookup
+ * related variable.
+ *
+ * Unboxing is supported by syntax (var).*
+ */
+ return InvalidOid;
+ }
I don't fully understand the above comments,
add
`elog(INFO, "%s:%d called", __FILE__, __LINE__); ` within the ELSE branch.
Then I found out the ELSE branch doesn't have coverage tests.

------------------<<>>>---------------
+ /*
+ * a.b.c can mean catalog.schema.variable or
+ * schema.variable.field.
....
+ /*
+ * a.b can mean "schema"."variable" or "variable"."field".
+ * Check both variants, and returns InvalidOid with
+ * not_unique flag, when both interpretations are
+ * possible.
+ */
here, we use the word "field", but the function IdentifyVariable above
comment, we use
word "attribute", for consistency's sake, we should use "attribute"
instead of "field"

+/* -----
+ * IdentifyVariable - try to find a variable from a list of identifiers
+ *
+ * Returns the OID of the variable found, or InvalidOid.
+ *
+ * "names" is a list of up to four identifiers; possible meanings are:
+ * - variable  (searched on the search_path)
+ * - schema.variable
+ * - variable.attribute  (searched on the search_path)
+ * - schema.variable.attribute
+ * - database.schema.variable
+ * - database.schema.variable.attribute

------------------<<>>>---------------