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From: Dmitry Koval <d.koval@postgrespro.ru>
To: andrewbille@gmail.com
To: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17385: "RESET transaction_isolation" inside serializable transaction causes Assert at the transaction end
Date: Fri, 28 Jan 2022 18:26:08 +0300
Message-ID: <b22395d2-d432-f211-0bed-1f466df75152@postgrespro.ru> (raw)
In-Reply-To: <17385-9ee529fb091f0ce5@postgresql.org>
References: <17385-9ee529fb091f0ce5@postgresql.org>

Hi,

Additional information. Query
"RESET transaction_isolation;"
in previous message can be replaced to synonym
"SET transaction_isolation=DEFAULT;"
(error will be the same).

I attached file with simple fix for branch "master".

I not sure that need to use a separate block of code for the
"transaction_isolation" GUC-variable. But this is a special variable
and there are several places in the code with handling of this variable.

With best regards,
Dmitry Koval.

Attachments:

v1-0001-Fixed-reset-transaction_isolation.patch (text/plain, 1.8K) download
diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
index e5ddcda0b4..038da968b6 100644
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -531,14 +531,16 @@ check_XactIsoLevel(int *newval, void **extra, GucSource source)
 		if (FirstSnapshotSet)
 		{
 			GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
-			GUC_check_errmsg("SET TRANSACTION ISOLATION LEVEL must be called before any query");
+			GUC_check_errmsg("%s TRANSACTION ISOLATION LEVEL must be called before any query",
+							 (source == PGC_S_OVERRIDE) ? "RESET" : "SET");
 			return false;
 		}
 		/* We ignore a subtransaction setting it to the existing value. */
 		if (IsSubTransaction())
 		{
 			GUC_check_errcode(ERRCODE_ACTIVE_SQL_TRANSACTION);
-			GUC_check_errmsg("SET TRANSACTION ISOLATION LEVEL must not be called in a subtransaction");
+			GUC_check_errmsg("%s TRANSACTION ISOLATION LEVEL must not be called in a subtransaction",
+							 (source == PGC_S_OVERRIDE) ? "RESET" : "SET");
 			return false;
 		}
 		/* Can't go to serializable mode while recovery is still active */
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 4c94f09c64..2ffd6fb844 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -8021,6 +8021,17 @@ set_config_option(const char *name, const char *value,
 					newextra = conf->reset_extra;
 					source = conf->gen.reset_source;
 					context = conf->gen.reset_scontext;
+
+					/*
+					 * Reseted transaction_isolation value can be not
+					 * applicable to current transaction
+					 */
+					if (strcmp(name, "transaction_isolation") == 0)
+					{
+						if (!call_enum_check_hook(conf, &newval, &newextra,
+												  source, elevel))
+							return 0;
+					}
 				}
 
 				if (prohibitValueChange)

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  Cc: d.koval@postgrespro.ru, andrewbille@gmail.com, pgsql-bugs@lists.postgresql.org
  Subject: Re: BUG #17385: "RESET transaction_isolation" inside serializable transaction causes Assert at the transaction end
  In-Reply-To: <b22395d2-d432-f211-0bed-1f466df75152@postgrespro.ru>

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