MDEV-19011 Assertion `file->s->base.reclength < file->s->vreclength' failed

The assertion is improved: storage engines like myisam always have to store
at least one field, so the assertion does not cover tables with no stored
columns.

mysql-test/suite/gcol/inc/gcol_keys.inc

@@ -809,4 +809,12 @@ eval LOAD DATA INFILE '$MYSQLTEST_VARDIR/tmp/load.data' REPLACE INTO TABLE t1 (p
 
 --remove_file $MYSQLTEST_VARDIR/tmp/load.data
 DROP TABLE t1;
+
+--echo # MDEV-19011 Assertion `file->s->base.reclength < file->s->vreclength'
+--echo # failed in ha_myisam::setup_vcols_for_repair
+CREATE TABLE t1 (a INT GENERATED ALWAYS AS (1) VIRTUAL) ENGINE=MyISAM;
+ALTER TABLE t1 ADD KEY (a);
+
+DROP TABLE t1;
+
 }

mysql-test/suite/gcol/r/gcol_keys_innodb.result

@@ -875,6 +875,11 @@ Warning	1264	Out of range value for column 'vi' at row 1
 LOAD DATA INFILE 'MYSQLTEST_VARDIR/tmp/load.data' REPLACE INTO TABLE t1 (pk,i,ts);
 ERROR 22003: Out of range value for column 'vi' at row 1
 DROP TABLE t1;
+# MDEV-19011 Assertion `file->s->base.reclength < file->s->vreclength'
+# failed in ha_myisam::setup_vcols_for_repair
+CREATE TABLE t1 (a INT GENERATED ALWAYS AS (1) VIRTUAL) ENGINE=MyISAM;
+ALTER TABLE t1 ADD KEY (a);
+DROP TABLE t1;
 #
 # BUG#21365158 WL8149:ASSERTION `!TABLE || (!TABLE->WRITE_SET
 #

mysql-test/suite/gcol/r/gcol_keys_myisam.result

@@ -877,6 +877,11 @@ Warning	1264	Out of range value for column 'vi' at row 1
 LOAD DATA INFILE 'MYSQLTEST_VARDIR/tmp/load.data' REPLACE INTO TABLE t1 (pk,i,ts);
 ERROR 22003: Out of range value for column 'vi' at row 1
 DROP TABLE t1;
+# MDEV-19011 Assertion `file->s->base.reclength < file->s->vreclength'
+# failed in ha_myisam::setup_vcols_for_repair
+CREATE TABLE t1 (a INT GENERATED ALWAYS AS (1) VIRTUAL) ENGINE=MyISAM;
+ALTER TABLE t1 ADD KEY (a);
+DROP TABLE t1;
 DROP VIEW  IF EXISTS v1,v2;
 DROP TABLE IF EXISTS t1,t2,t3;
 DROP PROCEDURE IF EXISTS p1;

storage/myisam/ha_myisam.cc

@@ -945,7 +945,8 @@ void ha_myisam::setup_vcols_for_repair(HA_CHECK *param)
       return;
     file->s->vreclength= new_vreclength;
   }
-  DBUG_ASSERT(file->s->base.reclength < file->s->vreclength);
+  DBUG_ASSERT(file->s->base.reclength < file->s->vreclength ||
+              !table->s->stored_fields);
   param->fix_record= compute_vcols;
   table->use_all_columns();
   table->vcol_set= &table->s->all_set;