panic when virtual columns evaluated in index merge reader

[eurekaka]

Development Task

Run the following test in UTF:

class IndexMergeComplicate(SimpleCase):
    name = "TICASE-1849"

    def run(self):
        self.execute_sql(
            "create table t(a int,b varchar(20),c datetime,d double,e int,f int as(a+b),key(a),key(b),key(c),key(d),key(e),key(f))")
        for i in range(20):
            if i < 5:
                self.execute_sql('''insert into t(a,b,e) values(null,"%d",null)''' % i)
            else:
                self.execute_sql('''insert into t(a,b,e) values(%d,null,%d)''' % (i, 20 - i))
        res = self.execute_sql("select /*+ use_index_merge(t)*/ e,f from t where t.e=3 or t.a=10")

panic would occur like:

[2020/05/08 19:28:45.550 +08:00] [ERROR] [index_merge_reader.go:662] ["panic in IndexMergeReaderExecutor indexMergeTableWorker: runtime error: index out of range [0] with length 0"] [conn=2]
panic: runtime error: index out of range [0] with length 0 [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x325fc3b]

goroutine 1642 [running]:
github.com/pingcap/tidb/executor.(*indexMergeTableScanWorker).handlePickAndExecTaskPanic.func1(0x3920580, 0xc001e4f140)
	/root/go/src/github.com/pingcap/tidb/executor/index_merge_reader.go:663 +0x19b
github.com/pingcap/tidb/util.WithRecovery.func1(0xc0015e2c60)
	/root/go/src/github.com/pingcap/tidb/util/misc.go:85 +0x7d
panic(0x3920580, 0xc001e4f140)
	/usr/local/go/src/runtime/panic.go:679 +0x1e0
github.com/pingcap/tidb/util/chunk.(*Column).GetString(0xc0011d3110, 0x0, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/util/chunk/column.go:528 +0x11b
github.com/pingcap/tidb/util/chunk.Row.GetString(0xc0015e6d20, 0x0, 0x0, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/util/chunk/row.go:70 +0x5c
github.com/pingcap/tidb/expression.(*Column).EvalString(0xc0015c2d20, 0x42db640, 0xc0019fed00, 0xc0015e6d20, 0x0, 0x0, 0x0, 0x4280000, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/expression/column.go:386 +0x2b0
github.com/pingcap/tidb/expression.(*builtinCastStringAsRealSig).evalReal(0xc0015c4e70, 0xc0015e6d20, 0x0, 0x0, 0x1a2dc00, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/expression/builtin_cast.go:1182 +0x260
github.com/pingcap/tidb/expression.(*ScalarFunction).EvalReal(0xc0015e05a0, 0x42db640, 0xc0019fed00, 0xc0015e6d20, 0x0, 0x0, 0x1142f00, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/expression/scalar_function.go:354 +0x83
github.com/pingcap/tidb/expression.(*builtinArithmeticPlusRealSig).evalReal(0xc0015c4d10, 0xc0015e6d20, 0x0, 0x0, 0x0, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/expression/builtin_arithmetic.go:289 +0x20c
github.com/pingcap/tidb/expression.(*ScalarFunction).EvalReal(0xc0015e05f0, 0x42db640, 0xc0019fed00, 0xc0015e6d20, 0x0, 0x0, 0x1142f00, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/expression/scalar_function.go:354 +0x83
github.com/pingcap/tidb/expression.(*ScalarFunction).Eval(0xc0015e05f0, 0xc0015e6d20, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/root/go/src/github.com/pingcap/tidb/expression/scalar_function.go:323 +0x3b5
github.com/pingcap/tidb/expression.(*Column).EvalVirtualColumn(0xc0015c3180, 0xc0015e6d20, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	/root/go/src/github.com/pingcap/tidb/expression/column.go:580 +0xc1
github.com/pingcap/tidb/executor.FillVirtualColumnValue(0xc002975dd8, 0x1, 0x1, 0xc001e4ef40, 0x1, 0x3, 0xc002a727b0, 0xc001fd31a0, 0x3, 0xc, ...)
	/root/go/src/github.com/pingcap/tidb/executor/executor.go:1728 +0x26e
github.com/pingcap/tidb/executor.(*TableReaderExecutor).Next(0xc000bd0840, 0x42a8b00, 0xc002f2d980, 0xc0015e6d20, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/executor/table_reader.go:171 +0x473
github.com/pingcap/tidb/executor.Next(0x42a8b00, 0xc002f2d980, 0x42b1400, 0xc000bd0840, 0xc0015e6d20, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/executor/executor.go:249 +0x5c7
github.com/pingcap/tidb/executor.(*indexMergeTableScanWorker).executeTask(0xc002f2d940, 0x42a8b00, 0xc002f2d980, 0xc0015f6480, 0x0, 0x0)
	/root/go/src/github.com/pingcap/tidb/executor/index_merge_reader.go:682 +0x51c
github.com/pingcap/tidb/executor.(*indexMergeTableScanWorker).pickAndExecTask(0xc002f2d940, 0x42a8b00, 0xc002f2d980, 0xc0015f6480)
	/root/go/src/github.com/pingcap/tidb/executor/index_merge_reader.go:650 +0x195
github.com/pingcap/tidb/executor.(*IndexMergeReaderExecutor).startIndexMergeTableScanWorker.func2.1()
	/root/go/src/github.com/pingcap/tidb/executor/index_merge_reader.go:398 +0x63
github.com/pingcap/tidb/util.WithRecovery(0xc0005b6780, 0xc0015e2c60)
	/root/go/src/github.com/pingcap/tidb/util/misc.go:93 +0x59
github.com/pingcap/tidb/executor.(*IndexMergeReaderExecutor).startIndexMergeTableScanWorker.func2(0xc002f2d940, 0x42a8b00, 0xc002f2d980, 0xc0015a5580, 0xc0022a3680)
	/root/go/src/github.com/pingcap/tidb/executor/index_merge_reader.go:397 +0xfd
created by github.com/pingcap/tidb/executor.(*IndexMergeReaderExecutor).startIndexMergeTableScanWorker
	/root/go/src/github.com/pingcap/tidb/executor/index_merge_reader.go:395 +0x377

[ChenPeng2013]

verified on
master: v4.0.0-beta.2-524-g73fe3ca4d
release-4.0: v4.0.0