chore: update flow dev guide #2184
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Signed-off-by: discord9 <[email protected]>
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Signed-off-by: discord9 <[email protected]>
Signed-off-by: discord9 <[email protected]>
Signed-off-by: discord9 <[email protected]>
nicecui
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Oct 31, 2025
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| ### Write a PromQL query | ||
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| GreptimeDB Flow also supports using PromQL for continuous aggregation, allowing you to leverage familiar PromQL syntax for time-series analysis. When writing PromQL queries for Flow, it's crucial to specify an `eval interval` as PromQL doesn't have a fixed time window. This interval determines how frequently the PromQL query is evaluated and new aggregated results are generated. |
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doesn't have a fixed time window?
does have a fixed time window?
| - `prom_aggregated` is the sink table that will store the continuously aggregated results. | ||
| - `TQL EVAL (start, end, '1m')` indicates that the PromQL query `rate(http_requests_total{job="my_service"}[1m])` is evaluated with a `step` of 1 minute. | ||
| - The `rate` function calculates the per-second average rate of increase of the `http_requests_total` metric over the last 1 minutes. | ||
| - The results, including the calculated `value` and the `timestamp` (which corresponds to the evaluation timestamp), are then written to the `rate_reqs` sink table. |
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When creating a PromQL flow, how to determine the sink table schema based on the flow?
| ## Architecture | ||
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| The batching mode consists of several key components that work together to achieve this continuous aggregation. | ||
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It is better to have a image to describe the architecture
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