Added info to mongodb

mongodb.md

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+# Mongodb
+
+**Get stats**  
+`mongo Health --eval "db.stats()" &>/dev/null`  
+
+**Query inline**  
+```shell
+second_ago=$(date --date="2 minutes ago" +%s)
+query="{class: 0, ts: {\$gt: ${second_ago} }}"
+mongo Health --eval "db.Stats.findOne($query).ts" &>/dev/null
+```
+
+## Export
+**Snapshot**  
+`mongodump --quiet -d User -o /data/snapshot/user-$(date +%Y%m%d)`
+
+**CSV**  
+`mongoexport --db Health --collection Stats --csv -q '{class: 1, type:"Customer"}' --fields sn,model_full,domain,cluster_serials,ts --out /tmp/data.csv`
+
+## Restore
+**Import from json** 
+`mongoimport -db HealthTS --collection CountTS --jsonArray --file count-ts.json`   
+
+**Import from snapshots**
+```shell
+restore_data()
+{
+  local reindex='db.getCollectionNames().forEach(function(col){db[col].reIndex()});'
+  mongorestore --db Health ./snapshot/Health/
+  mongorestore --db User ./snapshot/User/
+  mongo User --eval "$reindex" &>/dev/null
+  mongo Health --eval "$reindex" &>/dev/null  
+}
+```