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Pagination in RCOM Gateway

Pulling large datasets in one go is a bad design decision. It increases response time, overloads the database, and makes UIs unusable. Pagination fixes this by breaking data into manageable chunks.

In RCOM Gateway, this becomes even more important because:

  • Workflows execute per request → heavy queries directly impact system throughput
  • Event-driven processing means slow queries delay downstream logic
  • Custom UIs and APIs often deal with continuously growing datasets

Pagination ensures:

  • Faster response times
  • Lower database load
  • Scalable APIs
  • Predictable workflow execution

Pagination Approach (Limit + Offset)​

RCOM Gateway uses a standard pagination model:

  • Limit → number of records to fetch
  • Offset → starting position

Example API Call:

example.com/api/getdata?limit=10&offset=0

This means:

  • Fetch 10 records
  • Start from record 0

Step 1 — Define Workflow Parameters​

In your workflow, define:

NameType
LimitInt
OffsetInt

These will receive values from the API request.

Parameter Mapping

Parameter Mapping

Step 2 — Build Query Using SetVar​

Use SetVar to construct your SQL query.

Important correction:

  • Variable type should be String

Example:

"SELECT TC.\"OBJECT_ID\", TC.\"id\", TC.\"title\",  TC.\"status\", TC.\"author\", O.\"TIME_UPDATED\" \
FROM \"T_OGA_TCMS_Test_Cases\" TC \
JOIN \"T_OBJECT\" O ON TC.\"OBJECT_ID\"=O.\"OBJECT_ID\" \
ORDER BY O.\"TIME_UPDATED\" DESC, TC.\"id\" DESC \
LIMIT "+Limit+" OFFSET "+Offset+";"

Important Notes:

  • \" is required to escape quotes inside RCOM SQL strings
  • Query must remain a valid string
  • Do not overcomplicate with unnecessary casting
SetVar Example

SetVar Example

Step 3 — Execute Query​

Use:

  • CustomPostgresSQL
    • Input: Query string
    • Output: List<Dictionary<string, object>>

This returns paginated results.

CustomPostgresSQL Example

CustomPostgresSQL Example

Step 4 — Transform or Return Data​

Once data is retrieved you can further transform the data within the workflow or sned the data back via SetHttpResponse action.

Step 5 — Map URL Parameters in Event Processor​

After saving the workflow, map the URL parameters in the Event Processor → Variable Mapping:

Workflow VariableMapping Expression
LimitPARAMETERS["limit"].ToString().ToInt()
OffsetPARAMETERS["offset"].ToString().ToInt()

Key points:

  • Use contnet type as Dynamic.
  • URL params are available in PARAMETERS
  • Always cast to correct type
Event Processor Mapping

Event Processor Mapping

Example Flow​

Request:

GET /api/getdata?limit=20&offset=40

Query Behavior:

  • LIMIT 20 OFFSET 40

Result:

  • Records 41–60 returned