elasticsearch/docs/reference/esql/implicit-casting.asciidoc

[[esql-implicit-casting]]
=== {esql} implicit casting

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<titleabbrev>Implicit casting</titleabbrev>
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Often users will input `datetime`, `ip`, `version`, or geospatial objects as simple strings in their queries for use in predicates, functions, or expressions. {esql} provides <<esql-type-conversion-functions, type conversion functions>> to explicitly convert these strings into the desired data types.

Without implicit casting users must explicitly code these `to_X` functions in their queries, when string literals don't match the target data types they are assigned or compared to. Here is an example of using `to_datetime` to explicitly perform a data type conversion.

[source.merge.styled,esql]
----
FROM employees
| EVAL dd_ns1=date_diff("day", to_datetime("2023-12-02T11:00:00.00Z"), birth_date)
| SORT emp_no
| KEEP dd_ns1
| LIMIT 1
----

Implicit casting improves usability, by automatically converting string literals to the target data type. This is most useful when the target data type is `datetime`, `ip`, `version` or a geo spatial. It is natural to specify these as a string in queries.

The first query can be coded without calling the `to_datetime` function, as follows:

[source.merge.styled,esql]
----
FROM employees
| EVAL dd_ns1=date_diff("day", "2023-12-02T11:00:00.00Z", birth_date)
| SORT emp_no
| KEEP dd_ns1
| LIMIT 1
----

[float]
=== Implicit casting support

The following table details which {esql} operations support implicit casting for different data types.

[%header.monospaced.styled,format=dsv,separator=|]
|===
||ScalarFunction|BinaryComparison|ArithmeticOperation|InListPredicate|AggregateFunction
|DATETIME|Y|Y|Y|Y|N
|DOUBLE|Y|N|N|N|N
|LONG|Y|N|N|N|N
|INTEGER|Y|N|N|N|N
|IP|Y|Y|Y|Y|N
|VERSION|Y|Y|Y|Y|N
|GEO_POINT|Y|N|N|N|N
|GEO_SHAPE|Y|N|N|N|N
|CARTESIAN_POINT|Y|N|N|N|N
|CARTESIAN_SHAPE|Y|N|N|N|N
|BOOLEAN|Y|Y|Y|Y|N
|===