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/AWS DMS Postgres to OpenSearch LOB handling/

AWS DMS Postgres to OpenSearch LOB handling


Source: postgres Target: OpenSearch

I have a text column called description in one of my postgres tables. Per the documentation, this data type is mapped to a NCLOB. Since OpenSearch does not not offer LOB support, my description is missing in my OpenSearch documents.

I tried using the mapping rule bellow, but does not seem to be doing anything

    "rule-type": "transformation",
    "rule-id": "3",
    "rule-name": "3",
    "rule-target": "column",
    "object-locator": {
        "schema-name": "public",
        "table-name": "jobs",
        "column-name": "description"
    "rule-action": "change-data-type",
    "data-type": {
        "type": "string",
        "length": 500

When i check the logs i see the following

Column 'description' is unsupported in table def '' since the LOB support is disabled 

However, i do have LOB enabled under task settings:

"TargetMetadata": {
        "ParallelApplyBufferSize": 0,
        "ParallelApplyQueuesPerThread": 0,
        "ParallelApplyThreads": 0,
        "TargetSchema": "",
        "InlineLobMaxSize": 0,
        "ParallelLoadQueuesPerThread": 0,
        "SupportLobs": true,
        "LobChunkSize": 10,
        "TaskRecoveryTableEnabled": false,
        "ParallelLoadThreads": 0,
        "BatchApplyEnabled": false,
        "FullLobMode": true,
        "LimitedSizeLobMode": false,
        "LoadMaxFileSize": 0,
        "ParallelLoadBufferSize": 0

Is that transformation rule supposed to work? Or will any LOB column be skipped because OpenSearch does not have LOB support? Any way to make this work?


1 Answers

Transformation rules like - "rule-action": "change-data-type", work on DMS data types. "type": "string" , "length": 500 will be the DMS data type here which will be converted to the target engine data type. Since DMS does not support string as a data type for Opensearch target, this attribute is not getting converted. Please refer : AWS DMS data type - Boolean,Date,Time, Timestamp,INT4,Real4,UINT4 only supported DMS data types. No string data type allowed for Opensearch as a target

answered 4 months ago
  • How does it handle varchars? in the same table i have a name column which is a varchar(255) and that get's mapped to a string type in OpenSearch. Is there no way to migrate a text type from postgres to OpenSearch?

  • Yeah, it's confusing how DMS handles varchar even it is not mentioned in the documentation as supported source data type! I'm stuck in the same problem, did you find any solution?

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