HELP needed on the database size management

[Sixonlon]

Hi there,

Thanks for your library, very usefull. I'm currently building a web server that read the data stored in a firebase database but I would like to manage it in that way : I want to limit the max number of data (actually I upload JSON data) stored to a certain number. When I need to upload new data, I would like the oldest one to be deleted and then add the new one. I had the idea to add in my JSON object the firebase timestamp and then querry my datas by using the timestamp. I would store the information and then use it to delete the oldest node before uploading a new one.

I manage to upload my data with the timestamp but I'm stuck on the querry part. the way I structure my database is as followed : -key XXXXXXXXXX data : the actual data (an Integer) timestamp : the timestamp -key YYYYYYYYYY data : the actual data (an Integer) timestamp : the timestamp -key ZZZZZZZZZZ data : the actual data (an Integer) timestamp : the timestamp ....

Here is the code I use. What do I do wrong with the querry part ? Would there exist another way to do what I want ? I tough of generate a custom key instead of the random one generated automatically that name would be stored. I would then track the X latest name added and then delete the oldest one when I upload new data. But keeping track of that would be quite heavy in think.

Thanks in advance ;)

#include <Arduino.h>
#include <WiFi.h>
#include <FirebaseESP32.h>

#define FIREBASE_HOST "XXXXXXXXb.firebaseio.com"
#define FIREBASE_AUTH "SECRET"
#define WIFI_SSID "WIFI_SSID "
#define WIFI_PASSWORD "WIFI_PASSWORD "

byte rxindex = 0;
char rxdata[32];

//Define Firebase Data object
FirebaseData firebaseData;

void setup()
{
  Serial.begin(115200);
  Serial.println();
  Serial.println();

  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED)
  {
    Serial.print(".");
    delay(300);
  }
  Serial.println();
  Serial.print("Connected with IP: ");
  Serial.println(WiFi.localIP());
  Serial.println();

  Firebase.begin(FIREBASE_HOST, FIREBASE_AUTH);
  Firebase.reconnectWiFi(true);
}
void printResult(FirebaseData &data)
{
    if (data.dataType() == "int")
        Serial.println(data.intData());
    else if (data.dataType() == "float")
        Serial.println(data.floatData(), 5);
    else if (data.dataType() == "double")
        printf("%.9lf\n", data.doubleData());
    else if (data.dataType() == "boolean")
        Serial.println(data.boolData() == 1 ? "true" : "false");
    else if (data.dataType() == "string")
        Serial.println(data.stringData());
    else if (data.dataType() == "json")
    {
        Serial.println();
        FirebaseJson &json = data.jsonObject();
        //Print all object data
        Serial.println("Pretty printed JSON data:");
        String jsonStr;
        json.toString(jsonStr,true);
        Serial.println(jsonStr);
        Serial.println();
        Serial.println("Iterate JSON data:");
        Serial.println();
        size_t len = json.iteratorBegin();
        String key, value = "";
        int type = 0;
        for (size_t i = 0; i < len; i++)
        {
            json.iteratorGet(i, type, key, value);
            Serial.print(i);
            Serial.print(", ");
            Serial.print("Type: ");
            Serial.print(type == FirebaseJson::JSON_OBJECT ? "object" : "array");
            if (type == FirebaseJson::JSON_OBJECT)
            {
                Serial.print(", Key: ");
                Serial.print(key);
            }
            Serial.print(", Value: ");
            Serial.println(value);
        }
        json.iteratorEnd();
    }
    else if (data.dataType() == "array")
    {
        Serial.println();
        //get the array data from FirebaseData using FirebaseJsonArray object
        FirebaseJsonArray &arr = data.jsonArray();
        //Print all array values
        Serial.println("Pretty printed Array:");
        String arrStr;
        arr.toString(arrStr,true);
        Serial.println(arrStr);
        Serial.println();
        Serial.println("Iterate array values:");
        Serial.println();
        for (size_t i = 0; i < arr.size(); i++)
        {
            Serial.print(i);
            Serial.print(", Value: ");

            FirebaseJsonData &jsonData = data.jsonData();
            //Get the result data from FirebaseJsonArray object
            arr.get(jsonData, i);
            if (jsonData.typeNum == FirebaseJson::JSON_BOOL)
                Serial.println(jsonData.boolValue ? "true" : "false");
            else if (jsonData.typeNum == FirebaseJson::JSON_INT)
                Serial.println(jsonData.intValue);
            else if (jsonData.typeNum == FirebaseJson::JSON_FLOAT)
              Serial.println(jsonData.floatValue);
            else if (jsonData.typeNum == FirebaseJson::JSON_DOUBLE)
                printf("%.9lf\n", jsonData.doubleValue);
            else if (jsonData.typeNum == FirebaseJson::JSON_STRING ||
                     jsonData.typeNum == FirebaseJson::JSON_NULL ||
                     jsonData.typeNum == FirebaseJson::JSON_OBJECT ||
                     jsonData.typeNum == FirebaseJson::JSON_ARRAY)
                Serial.println(jsonData.stringValue);
        }
    }
    else
    {
      Serial.println(data.payload());
    }
}

void Querrying(){
  QueryFilter query;

  query.orderBy("Timestamp");
  query.startAt(0);
  query.endAt(firebaseData.doubleData());
  query.limitToLast(8);

  //Begin the data filtering test
  Serial.println("------------------------------------");
  Serial.println("Data Filtering test...");

  if (Firebase.getJSON(firebaseData, "/Volume", query))
  {

    Serial.println("PASSED");
    Serial.println("JSON DATA: ");
    printResult(firebaseData);
    Serial.println("------------------------------------");
    Serial.println();
  }
  else
  {
    Serial.println("FAILED");
    Serial.println("REASON: " + firebaseData.errorReason());
    Serial.println("------------------------------------");
    Serial.println();
  }

  //Clear all query parameters
  query.clear();

}

void process_command(char *command){
  String path = "/Test";
  FirebaseJson Package;

  char *cmd;
  cmd = strtok(command, " \r");

  // Bit of code adding data to Databese (called here firebaseData) and the server timestamp
  if (strcmp(cmd, "11") == 0){
    String access;
    cmd = strtok(NULL, " \r");
    Serial.println("------------------------------------");
    Serial.println(" ## Add new data");
    Package.clear();
    Package.add("Donnee",11);
    Package.add("Timestamp");
    if(Firebase.pushJSON(firebaseData, "/Volume", Package)){
      Serial.print("Node added : ");
      access = firebaseData.pushName();
      Serial.println(access);
    }
    else{
      Serial.println(firebaseData.errorReason());
    }

    Serial.println(" ## Set Timestamp test...");
    if (Firebase.pushTimestamp(firebaseData, "Volume/"+access+"/Timestamp"))
    {
      Serial.println("PASSED");
      Serial.println("PATH: " + firebaseData.dataPath());
      Serial.println("------------------------------------");
      Serial.println();
    }
    else
    {
      Serial.println("FAILED");
      Serial.println("REASON: " + firebaseData.errorReason());
      Serial.println("------------------------------------");
      Serial.println();
    }
  } else 
  if (strcmp(cmd, "12") == 0){
    String access;
    cmd = strtok(NULL, " \r");
    Serial.println("------------------------------------");
    Serial.println(" ## Add new data");
    Package.clear();
    Package.add("Donnee",12);
    Package.add("Timestamp");
    if(Firebase.pushJSON(firebaseData, "/Volume", Package)){
      Serial.print("Node added : ");
      access = firebaseData.pushName();
      Serial.println(access);
    }
    else{
      Serial.println(firebaseData.errorReason());
    }

    Serial.println(" ## Set Timestamp test...");
    if (Firebase.pushTimestamp(firebaseData, "Volume/"+access+"/Timestamp"))
    {
      Serial.println("PASSED");
      Serial.println("PATH: " + firebaseData.dataPath());
      Serial.println("------------------------------------");
      Serial.println();
    }
    else
    {
      Serial.println("FAILED");
      Serial.println("REASON: " + firebaseData.errorReason());
      Serial.println("------------------------------------");
      Serial.println();
    }
  }else 
  if(strcmp(cmd,"querry")==0){
    Serial.println("--------------------------");
    Serial.println("Querying begins");
    Querrying();

  }
  {
    Serial.print(F("Unknown command\n"));
  }
}

void loop()
{
  // Handle the serial in
  if(Serial.available()>0)
  {
    rxdata[rxindex]= Serial.read();
     if (rxdata[rxindex] == '\r'){ //return
      Serial.print(F("\n"));
      rxdata[rxindex] = '\0';

      process_command(rxdata);
      rxindex = 0;
    } else if (rxdata[rxindex] == '\b')
    { //backspace
      if (rxindex > 0)
      {
        Serial.print(F("\b \b"));
        rxindex--;
      }
    }
    else  //other char
    {
      Serial.print(rxdata[rxindex]);
      rxindex++;
      if (rxindex >= 32)
      {
        rxindex = 0;
      }
    }
  }
  // put the rest of the code here
}

[mobizt]

You need to set the .indexOn in the database rules to the parent node with the name of child node to be queried.

Please see this example.

[Sixonlon]

Thks man!