gdb returns result when cache set failed

[qinyuguang]

gdb缓存挂掉时候，查询操作应返回db数据，而不是返回设置缓存时的error

[gqcn]

@qinyuguang 不能丢弃方法中的任何error

[qinyuguang]

@gqcn 比如这样一段代码，怎么判断是db错误，还是cache错误呢？

任意一种错误，结果返回的都是 count=0 且 err!=nil

func cache(ctx context.Context) {
	count, err := g.DB().Model("test").Ctx(ctx).
		Cache(gdb.CacheOption{Duration: 10 * time.Minute, Name: "count"}).
		Count()

	if err != nil {
		// cache错误？db错误？
	}

}

此时，给调用者返回错误呢，还是数据呢？（这个例子Count方法返回0大概还是个bug，执行了sql去查应该有数据的）

如果查询db有结果还好，可以按照结果不为空再进行一次判断，来确认是否cache错误。如果查询db是空结果，那就没法判断是什么错误了

[qinyuguang]

额，实际上在cache挂掉时，scan出来的结果其实都是nil

func cache2(ctx context.Context) {
	type test struct {
		ID int
	}

	var res *test
	if err := g.DB().
		Model("test").
		Ctx(ctx).
		Cache(gdb.CacheOption{Duration: 10 * time.Minute, Name: "cache2"}).
		Scan(&res); err != nil {
		g.Log().Debug(ctx, "err:", err)
	}

	g.Log().Debugf(ctx, "res: %#v", res)
}

输出

2022-03-11 00:03:07.657 [DEBU] {38a479fb7510db16d7d2476587313fac} [  7 ms] [default] [rows:1  ] SELECT "id" FROM "test" LIMIT 1 
2022-03-11 00:03:07.657 [DEBU] err: Redis Client Do failed with arguments "[SETEX cache2 600 [91 123 34 105 100 34 58 49 125 93]]": dial tcp 127.0.0.1:6379: connect: connection refused 
2022-03-11 00:03:07.657 [DEBU] res: (*main.test)(nil) 

[gqcn]

换个名字，例如cacheErr，同样的，上面的cacheObj.Remove的err也改一下名字。

[codecov-commenter]

Codecov Report

Merging #1660 (4d24ac6) into master (ba7cbfe) will increase coverage by 0.07%.
The diff coverage is 0.00%.

❗ Current head 4d24ac6 differs from pull request most recent head a4ab9c2. Consider uploading reports for the commit a4ab9c2 to get more accurate results

@@            Coverage Diff             @@
##           master    #1660      +/-   ##
==========================================
+ Coverage   71.47%   71.55%   +0.07%     
==========================================
  Files         445      445              
  Lines       42544    42674     +130     
==========================================
+ Hits        30410    30534     +124     
- Misses      10237    10248      +11     
+ Partials     1897     1892       -5     

Flag	Coverage Δ
go-1.15	71.53% <0.00%> (+0.08%)	⬆️
go-1.16	71.51% <0.00%> (+0.07%)	⬆️
go-1.17	71.53% <0.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
database/gdb/gdb_model_select.go	72.25% <0.00%> (ø)
internal/utils/utils_reflect.go	38.59% <0.00%> (-26.11%)	⬇️
os/gspath/gspath_cache.go	84.21% <0.00%> (-3.51%)	⬇️
os/gcron/gcron_z_unit_schedule.go	67.09% <0.00%> (-0.43%)	⬇️
os/glog/glog_logger_rotate.go	67.31% <0.00%> (+1.46%)	⬆️
util/gutil/gutil_dump.go	88.08% <0.00%> (+8.08%)	⬆️
os/gstructs/gstructs_field.go	64.73% <0.00%> (+8.16%)	⬆️

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[qinyuguang]

@gqcn 已修改