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commit    d1fc0f382da15d2901bb740d9dfdd6be6488a1e4
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Wed Jun 21 15:07:11 2023 +0000
First released in: 16.0, 11.21, 12.16, 13.12, 14.9, 15.4

    Avoid Assert failure when processing empty statement in aborted xact.
    
    exec_parse_message() wants to create a cached plan in all cases,
    including for empty input.  The empty-input path does not have
    a test for being in an aborted transaction, making it possible
    that plancache.c will fail due to trying to do database lookups
    even though there's no real work to do.
    
    One solution would be to throw an aborted-transaction error in
    this path too, but it's not entirely clear whether the lack of
    such an error was intentional or whether some clients might be
    relying on non-error behavior.  Instead, let's hack plancache.c
    so that it treats empty statements with the same logic it
    already had for transaction control commands, ensuring that it
    can soldier through even in an already-aborted transaction.
    
    Per bug #17983 from Alexander Lakhin.  Back-patch to all
    supported branches.
    
    Discussion: https://postgr.es/m/17983-da4569fcb878672e@postgresql.org


 src/backend/utils/cache/plancache.c |  4 +++-
 src/test/regress/expected/psql.out  | 11 +++++++++++
 src/test/regress/sql/psql.sql       |  8 ++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 75b475c179b..b481cac5566 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -78,9 +78,11 @@
 /*
  * We must skip "overhead" operations that involve database access when the
  * cached plan's subject statement is a transaction control command.
+ * For the convenience of postgres.c, treat empty statements as control
+ * commands too.
  */
 #define IsTransactionStmtPlan(plansource)  \
-	((plansource)->raw_parse_tree && \
+	((plansource)->raw_parse_tree == NULL || \
 	 IsA((plansource)->raw_parse_tree->stmt, TransactionStmt))
 
 /*
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index dfa520671c0..9a7d43397ae 100644
--- a/src/test/regress/expected/psql.out
+++ b/src/test/regress/expected/psql.out
@@ -237,6 +237,17 @@ SELECT 3 AS x, 'Hello', 4 AS y, true AS "dirty\name" \gdesc \g
  3 | Hello    | 4 | t
 (1 row)
 
+-- test for server bug #17983 with empty statement in aborted transaction
+set search_path = default;
+begin;
+bogus;
+ERROR:  syntax error at or near "bogus"
+LINE 1: bogus;
+        ^
+;
+\gdesc
+The command has no result, or the result has no columns.
+rollback;
 -- \gexec
 create temporary table gexec_test(a int, b text, c date, d float);
 select format('create index on gexec_test(%I)', attname)
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index f662879da51..e6edf1ca0d1 100644
--- a/src/test/regress/sql/psql.sql
+++ b/src/test/regress/sql/psql.sql
@@ -119,6 +119,14 @@ SELECT 1 AS x, 'Hello', 2 AS y, true AS "dirty\name"
 -- all on one line
 SELECT 3 AS x, 'Hello', 4 AS y, true AS "dirty\name" \gdesc \g
 
+-- test for server bug #17983 with empty statement in aborted transaction
+set search_path = default;
+begin;
+bogus;
+;
+\gdesc
+rollback;
+
 -- \gexec
 
 create temporary table gexec_test(a int, b text, c date, d float);


[parent: 43090e1e7059]