Time Series Database:Use the SDK multi-value data model to read data

How it works

Build a query in three steps:

1. Create one MultiFieldSubQueryDetails object per field. Each specifies the field name, aggregator, and downsampling interval.

2. Create a MultiFieldSubQuery that groups the field details under a metric name and applies an optional tag filter.

3. Create a MultiFieldQuery with the time range and the subquery, then call tsdb.multiFieldQuery(query).

Query multi-value data

The following example queries three specific fields (speed, level, temperature) and all fields using MAX and MIN aggregators. Results are filtered by the district tag.

// Step 1: Define field-level query details.
// Each MultiFieldSubQueryDetails specifies a field, aggregator, and downsampling interval.
MultiFieldSubQueryDetails speedFieldDetails = MultiFieldSubQueryDetails
        .field("speed").aggregator(Aggregator.SUM).downsample("2s-sum").build();
MultiFieldSubQueryDetails levelFieldDetails = MultiFieldSubQueryDetails
        .field("level").aggregator(Aggregator.AVG).downsample("2s-avg").build();
MultiFieldSubQueryDetails tempFieldDetails = MultiFieldSubQueryDetails
        .field("temperature").aggregator(Aggregator.COUNT).downsample("2s-count").build();
// Use "*" to query all fields. Set an alias to distinguish results when multiple
// wildcard queries are included.
MultiFieldSubQueryDetails allFieldsDetails1 = MultiFieldSubQueryDetails
        .field("*").aggregator(Aggregator.MAX).downsample("2s-max").alias("max_").build();
MultiFieldSubQueryDetails allFieldsDetails2 = MultiFieldSubQueryDetails
        .field("*").aggregator(Aggregator.MIN).downsample("2s-min").alias("min_").build();

List<MultiFieldSubQueryDetails> subQueryDetails = new LinkedList<>();
subQueryDetails.add(speedFieldDetails);
subQueryDetails.add(levelFieldDetails);
subQueryDetails.add(tempFieldDetails);
subQueryDetails.add(allFieldsDetails1);
subQueryDetails.add(allFieldsDetails2);

// Step 2: Create a subquery for the multi-value data model.
// Specify the metric, the field details list, and an optional tag filter.
MultiFieldSubQuery subQuery = MultiFieldSubQuery.metric(metric).fieldsInfo(subQueryDetails)
        .filter(Filter.filter(FilterType.LiteralOr, "district", "Yuhang|Xiacheng|Xihu", true).build())
        .build();

// Step 3: Set the time range and run the query.
MultiFieldQuery query = MultiFieldQuery.start(1542772000L).end(1542772020L).msResolution(false)
        .sub(subQuery).build();

List<MultiFieldQueryResult> results = tsdb.multiFieldQuery(query);

Parameters