How to extract number from a string in mongodb query? - mongodb

Question

The only problem with commented query is that "$DAMAGE_PROPERTY" is written in 0K, 1K, 250K, 5.20M format, and the $todecimal/$toDouble aren't able to convert that to an integer. My purpose is to extract number out of string in the query itself and not iterate over the result array.
try {
const db = client.db(dbName);
let collection = db.collection("Storm");
let query = {
STATE: "INDIANA",
EVENT_TYPE: event,
DAMAGE_PROPERTY: { $nin: ["", null] },
YEAR: { $gte: startYear, $lte: endYear },
};
// --> aggregation failed.
// let res = await collection
// .aggregate([
// { $match: query },
// {
// $project: {
// document: "$$ROOT",
// damage: {
// $sum: {
// $toDouble: "$DAMAGE_PROPERTY", //Cause of Error: no conversion
// },
// },
// },
// },
// ])
// .toArray();
// console.log(res);
// ---> Solution I want to avoid
let res = await collection.find(query).toArray();
var totalDamage = 0;
for (let i = 0; i < res.length; i++) {
totalDamage += parseFloat(res[i].DAMAGE_PROPERTY);
}
console.log(
`Total Damage to property in Indiana from ${startYear} to ${endYear} due to ${event} is ${totalDamage}K`
);
} catch (err) {
console.log(err);
} finally {
client.close();
}
Test Data in json:
{
"BEGIN_YEARMONTH": 200809,
"BEGIN_DAY": 14,
"BEGIN_TIME": 830,
"END_YEARMONTH": 200809,
"END_DAY": 14,
"END_TIME": 1030,
"EPISODE_ID": 21247,
"YEAR": 2008,
"DEATHS_DIRECT": 0,
"DEATHS_INDIRECT": 0,
"DAMAGE_PROPERTY": "5.20M",
},

Answer 1

Providing another solution to avoid clutter/confuse, Answer #1:
db.collection.aggregate([
{
$group: {
_id: null,
DAMAGE_PROPERTY: {
$push: {
$let: {
vars: {
damage: {
$toDouble: {
$substrBytes: ["$DAMAGE_PROPERTY", 0, { $subtract: [{ $strLenCP: "$DAMAGE_PROPERTY" }, 1] }]
}
},
unit: {
$substrBytes: ["$DAMAGE_PROPERTY", { $subtract: [{ $strLenCP: "$DAMAGE_PROPERTY" }, 1] }, 1]
}
},
in: {
$switch: {
branches: [
{
case: { $eq: ["$$unit", "M"] },
then: {
$multiply: ["$$damage", 100]
}
},
{
case: { $eq: ["$$unit", "K"] },
then: {
$multiply: ["$$damage", 10]
}
},
// You can have more cases in future
],
default: "Error: No unit matched." // or 0
}
}
}
}
}
}
},
{
$project: {
_id: 0,
totalDamage: { $sum: "$DAMAGE_PROPERTY" }
}
}
]);
Output:
{
"totalDamage" : 615
}

Answer 2

UPDATE based on coments:
db.collection.aggregate([
{
$group: {
_id: null,
DAMAGE_PROPERTY: {
$push: {
$cond: {
if: { $lt: [{ $size: { $split: ["$DAMAGE_PROPERTY", "K"] } }, 2] },
then: {
$multiply: [
{
$toDouble: { $first: { $split: ["$DAMAGE_PROPERTY", "M"] } }
},
100
]
},
else: {
$multiply: [
{
$toDouble: { $first: { $split: ["$DAMAGE_PROPERTY", "K"] } }
},
10
]
}
}
}
}
}
},
{
$project: {
_id: 0,
totalDamage: { $sum: "$DAMAGE_PROPERTY" }
}
}
]);
Output for the updated query
{
"totalDamage" : 615
}
What is $cond doing?
STEP 1: Try to split DAMAGE_PROPERTY by "K".
// Example 1: split_result = ["5.2M"]
// Example 2: split_result = ["9.5", ""]
if the length of split_result array is less than 2:
Try to split DAMAGE_PROPERTY by "M"
// For example: split_result = ["5.2", ""]
typecast the first string to decimal
return the result
else:
Split the DAMAGE_PROPERTY by "K"
// For example: split_result = ["9.5", ""]
typecast the first string to decimal
return the result
Try this:
db.collection.aggregate([
{
$group: {
_id: null,
DAMAGE_PROPERTY: {
$push: {
$toDouble: {
$cond: {
if: { $lt: [{ $size: { $split: ["$DAMAGE_PROPERTY", "K"] } }, 2] },
then: { $first: { $split: ["$DAMAGE_PROPERTY", "M"] } },
else: { $first: { $split: ["$DAMAGE_PROPERTY", "K"] } }
}
}
}
}
}
},
{
$project: {
_id: 0,
totalDamage: { $sum: "$DAMAGE_PROPERTY" }
}
}
]);
Output:
{
"totalDamage" : 14.7
}
Test data:
/* 1 createdAt:3/12/2021, 3:22:08 PM*/
{
"_id" : ObjectId("604b39c84b5860176c2254e2"),
"DAMAGE_PROPERTY" : "5.20M"
},
/* 2 createdAt:3/12/2021, 3:22:08 PM*/
{
"_id" : ObjectId("604b39c84b5860176c2254e3"),
"DAMAGE_PROPERTY" : "9.5K"
}