misleading error message in ProcessUtilitySlow T_CreateStatsStmt

jian he <jian.universality@gmail.com>

From: jian he <jian.universality@gmail.com>

To: PostgreSQL-development <pgsql-hackers@postgresql.org>

Date: 2025-08-21T11:59:14Z

Lists: pgsql-hackers

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

CREATE STATISTICS: improve misleading error message
- cbd3732cbbaa 14.20 landed
- 4529861cc408 15.15 landed
- f30c04682cdf 16.11 landed
- f9b41f3e1ecd 17.7 landed
- 38883916e41c 18.0 landed
- 9ec0b29976b6 19 (unreleased) landed
- f9a7622483c3 15.15 landed
- f225473cbae2 19 (unreleased) landed
- e9fb314c7ad8 17.7 landed
- d84a6c3dad1f 16.11 landed
- b830f9d67463 14.20 landed
- 3eea4dc2c7cf 18.0 landed
Glossary: improve definition of "relation"
- 16a9165ce4a4 19 (unreleased) landed
Extended statistics on expressions
- a4d75c86bf15 14.0 cited

hi.

while reviewing other work, some error messages in src/backend/tcop/utility.c
seem not accurate.

static void
ProcessUtilitySlow(ParseState *pstate,
                   PlannedStmt *pstmt,
                   const char *queryString,
                   ProcessUtilityContext context,
                   ParamListInfo params,
                   QueryEnvironment *queryEnv,
                   DestReceiver *dest,
                   QueryCompletion *qc)

            case T_CreateStatsStmt:
                {
                    Oid            relid;
                    CreateStatsStmt *stmt = (CreateStatsStmt *) parsetree;
                    RangeVar   *rel = (RangeVar *) linitial(stmt->relations);

                    if (!IsA(rel, RangeVar))
                        ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("only a single relation is
allowed in CREATE STATISTICS")));
                    relid = RangeVarGetRelid(rel,
ShareUpdateExclusiveLock, false);
                    /* Run parse analysis ... */
                    stmt = transformStatsStmt(relid, stmt, queryString);
                    address = CreateStatistics(stmt);
                }


for example:

create or replace function tftest(int) returns table(a int, b int) as $$
begin
  return query select $1, $1+i from generate_series(1,5) g(i);
end;
$$ language plpgsql immutable strict;

CREATE STATISTICS alt_stat2 ON a, b FROM tftest(1);
ERROR:  only a single relation is allowed in CREATE STATISTICS

this error message seem misleading?
also this error check seems duplicated in CreateStatistics?