Go语言mgo查询构建：深入理解bson.M与日期范围查询的正确实践

package main

import (
    "fmt"
    "time"

    "gopkg.in/mgo.v2/bson"
)

func main() {
    paramsPost := map[string][]string{
        "title":     {"example"},
        "from_date": {"2023-01-01"},
        "to_date":   {"2023-01-31"},
    }

    conditions := make(bson.M, 0)
    conditions["status"] = bson.M{"$ne": "delete"} // 初始条件：状态不为"delete"

    if item, ok := paramsPost["title"]; ok {
        if item[0] != "" {
            conditions["title"] = bson.RegEx{Pattern: item[0]} // 标题模糊匹配
        }
    }

    if item, ok := paramsPost["from_date"]; ok {
        if item[0] != "" {
            conditions["publishdate"] = bson.M{} // 错误：这里将publishdate键赋值为一个空的bson.M{}，但其类型被推断为interface{}
            fromDate, _ := time.Parse("2006-01-02", item[0])
            // 错误：试图在类型为interface{}的conditions["publishdate"]上进行map索引操作
            conditions["publishdate"]["$gte"] = fromDate.Unix() 
        }
    }

    if item, ok := paramsPost["to_date"]; ok {
        // 错误：同样可能导致问题，因为conditions["publishdate"]可能仍然是interface{}
        if _, ok := conditions["publishdate"]; !ok { 
            conditions["publishdate"] = bson.M{}
        }
        if item[0] != "" {
            toDate, _ := time.Parse("2006-01-02", item[0])
            // 错误：试图在类型为interface{}的conditions["publishdate"]上进行map索引操作
            conditions["publishdate"]["$lte"] = toDate.Unix() 
        }
    }

    fmt.Printf("Generated Conditions: %+v\n", conditions)
    // 运行上述代码会产生类似以下错误：
    // invalid operation: conditions["publishdate"]["$gte"] (index of type interface {})
}

// 假设 conditions["publishdate"] 已经被赋值为 interface{}(bson.M{})
if val, ok := conditions["publishdate"].(bson.M); ok {
    val["$gte"] = fromDate.Unix()
    conditions["publishdate"] = val // 确保将修改后的map重新赋值回去
}

package main

import (
    "fmt"
    "time"

    "gopkg.in/mgo.v2/bson"
)

func main() {
    paramsPost := map[string][]string{
        "title":     {"example title"},
        "from_date": {"2023-01-01"},
        "to_date":   {"2023-01-31"},
    }

    conditions := make(bson.M) // 使用make(bson.M) 初始化主查询条件map
    conditions["status"] = bson.M{"$ne": "delete"}

    // 处理标题模糊查询
    if item, ok := paramsPost["title"]; ok && item[0] != "" {
        conditions["title"] = bson.RegEx{Pattern: item[0], Options: "i"} // i表示不区分大小写
    }

    // 独立构建publishdate的条件map
    publishDateConditions := bson.M{} 

    if item, ok := paramsPost["from_date"]; ok && item[0] != "" {
        fromDate, err := time.Parse("2006-01-02", item[0])
        if err == nil {
            publishDateConditions["$gte"] = fromDate.Unix()
        } else {
            fmt.Printf("解析起始日期出错: %v\n", err)
        }
    }

    if item, ok := paramsPost["to_date"]; ok && item[0] != "" {
        toDate, err := time.Parse("2006-01-02", item[0])
        if err == nil {
            // 将结束日期设置为当天的最后一秒，确保包含整天
            publishDateConditions["$lte"] = toDate.Add(24*time.Hour - 1*time.Second).Unix()
        } else {
            fmt.Printf("解析结束日期出错: %v\n", err)
        }
    }

    // 如果publishDateConditions不为空，则将其添加到主查询条件中
    if len(publishDateConditions) > 0 {
        conditions["publishdate"] = publishDateConditions
    }

    fmt.Printf("最终生成的查询条件: %+v\n", conditions)

    // 示例输出：
    // 最终生成的查询条件: map[publishdate:map[$gte:1672531200 $lte:1675209599] status:map[$ne:delete] title:{Pattern:example title Options:i}]
}