Check if a record exists in a Julia array

Question

Say we have a matrix:

A = [1.0 2.0 3.0; 4.0 5.0 6.0] #2×3 Matrix{Float64}

and a record:

b = [1.0 2.0 3.0] #1×3 Matrix{Float64}

what is the most efficient way to check if record b exists in matrix A in Julia?

Doing b in A returns false.

And writing a nested for-loop when we may have a large matrix (many dimensions and many rows) to check seems inefficient.

Answer 1

For a 2D matrix like your example, the check is simple.

vec(b) in eachrow(A)
true

For large nD arrays, one can use

vec(b) in eachslice(A, dims=1)
true

Answer 2

If the rows in the matrix are unsorted I would just do:

findfirst(==(vec(b)), eachrow(A))

If the rows are sorted (which is recommended when you do the search many times) I would consider using searchsorted over a vector of views of array rows.