spark-instrumented-optimizer/sql/catalyst
Maxim Gekk 776f299fc8 [SPARK-24709][SQL] schema_of_json() - schema inference from an example
## What changes were proposed in this pull request?

In the PR, I propose to add new function - *schema_of_json()* which infers schema of JSON string literal. The result of the function is a string containing a schema in DDL format.

One of the use cases is using of *schema_of_json()* in the combination with *from_json()*. Currently, _from_json()_ requires a schema as a mandatory argument. The *schema_of_json()* function will allow to point out an JSON string as an example which has the same schema as the first argument of _from_json()_. For instance:

```sql
select from_json(json_column, schema_of_json('{"c1": [0], "c2": [{"c3":0}]}'))
from json_table;
```

## How was this patch tested?

Added new test to `JsonFunctionsSuite`, `JsonExpressionsSuite` and SQL tests to `json-functions.sql`

Author: Maxim Gekk <maxim.gekk@databricks.com>

Closes #21686 from MaxGekk/infer_schema_json.
2018-07-04 09:38:18 +08:00
..
src [SPARK-24709][SQL] schema_of_json() - schema inference from an example 2018-07-04 09:38:18 +08:00
pom.xml [SPARK-19550][BUILD][FOLLOW-UP] Remove MaxPermSize for sql module 2018-01-15 07:49:34 -06:00