SQLInterface relies upon more schema information than is normally able to be
provided by a raw SQL schema. For instance, information about the original
non-canonicalized name of a field gets lost when that field is normalized into
a column.
To achieve this, metadata is stored. For Target Postgres, this metadata is currently stored in a JSON Blob which is set onto each table's comment.
This document details the structure of this structure.
| Field | Type | Default | Details |
|---|---|---|---|
version |
["string", "null"] |
null |
The Singer table version to be used with activate_version |
key_properties |
["array", "null"] |
null |
Array of strings representing the pks for the table. |
mappings |
["object", "null"] |
null |
Mappings which take current_column_name to a COLUMN_MAPPING detailed below. |
table_mappings |
{'type': ["array", "null"], 'items': {'type': "$TABLE_MAPPING"}} |
null |
Mappings which detail information about tables and their names. See TABLE_MAPPING below. |
| Field | Type | Default | Details |
|---|---|---|---|
from |
["string"] |
N/A |
The original name of the field/property this column represents |
type |
["array"] |
N/A |
The json_schema.type of the from column |
| Field | Type | Default | Details |
|---|---|---|---|
type |
["string"] |
TABLE |
The type of mapping present, which is always TABLE |
from |
{'type': ["array"], 'items': {'type': ["string"]}} |
[] |
The fields/properties which lead to this (sub)table in the original schema. ie, the root table's path will always be [<stream-name>], a table made from an array found at the property foo will be [<stream-name>, "foo"] etc. etc. |
to |
["string"] |
N/A |
The table name which takes the from path to the target's representation |