In MongoDB, How To Perform Query Based On If One String Field Contains Another

Hello please help me with this. In mongodb, I have a collection like this: data1= { 'string1':'abc', 'string2':'abcde' } data2= { 'string1':'abc', 'string2':'ftgr'

Solution 1:

You can do this with $where by creating a RegExp for string1 and then testing it against string2:

db.test.find({$where: 'RegExp(this.string1).test(this.string2)'})

However, if you're using MongoDB 3.4+ you can do this more efficiently by using the $indexOfCP aggregation operator:

db.test.aggregate([
    // Project  the index of where string1 appears in string2, along with the original doc.
    {$project: {foundIndex: {$indexOfCP: ['$string2', '$string1']}, doc: '$$ROOT'}},
    // Filter out the docs where the string wasn't found
    {$match: {foundIndex: {$ne: -1}}},
    // Promote the original doc back to the root
    {$replaceRoot: {newRoot: '$doc'}}
])

Or more directly by also using $redact:

db.test.aggregate([
    {$redact: {
        $cond: {
            if: { $eq: [{$indexOfCP: ['$string2', '$string1']}, -1]},
            then: '$$PRUNE',
            else: '$$KEEP'
        }
    }}
])