db.COLLECTION_NAME.aggregate([
{$addFields: {
"CONCATENATED_STRING": {$reduce: {
"input": "$ARRAY_OF_STRINGS_FIELD_NAME",
"initialValue": "",
"in": {
"$concat": [
"$$value",
{"$cond": [{"$eq": ["$$value", ""]}, "", ", "]},
"$$this"
]
}
}}
}}
]);
2023-03-29
MongoDB - Array of strings to comma-separated string
db.COLLECTION_NAME.aggregate([
{$addFields: {
"CONCATENATED_STRING": {$reduce: {
"input": "$ARRAY_OF_STRINGS_FIELD_NAME",
"initialValue": "",
"in": {
"$concat": [
"$$value",
"$$this",
", ",
]
}
}}
}}
]);
2023-02-22
Minimongo - How to cast a date typed as an object, to an actual date type
db.COLLECTION.update(
{
$expr: {$eq: [{"$type": "$YOUR_DATE_FIELD"}, "object"]},
},
{$set: {
"YOUR_DATE_FIELD": new Date(parseInt("$YOUR_DATE_FIELD.$date.$numberLong")),
}},
{
multi: true,
upsert: false,
}
);
Original issue:
Uncaught MinimongoError: Key $date must not start with '$'
2023-01-18
MongoDB - Count the number of fields or keys in a sub-document
db.COLLECTION_NAME.aggregate([
{$addFields: {
'SUB_DOCUMENT_FIELD_COUNT':
{$size:
{$objectToArray:
{$ifNull: [
"$YOUR_FIELD",
{}
]}
}
},
}},
]);
MongoDB - Count the number of fields or keys in a document
db.COLLECTION_NAME.aggregate([
{$addFields: {
'THIS_DOCUMENT_KEY_COUNT': {$size: {$objectToArray: "$$ROOT"}},
}},
]);
2023-01-08
Python - How to create a dataframe with a matrix of random numbers
import pandas as pd
import numpy as np
from tabulate import tabulate
# 100 rows, 3 columns, random numbers
df = pd.DataFrame(
np.random.rand(100, 3),
columns=['COLUMN_1', 'COLUMN_2', 'COLUMN_3']
)
# Pretty-print it
print(tabulate(df, headers='keys', tablefmt='grid', showindex='always'))
2023-01-07
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