func (e *StatementExecutor) createIterators(stmt *influxql.SelectStatement, ctx *influxql.ExecutionContext) ([]influxql.Iterator, *influxql.SelectStatement, error) {
// It is important to "stamp" this time so that everywhere we evaluate `now()` in the statement is EXACTLY the same `now`
now := time.Now().UTC()
opt := influxql.SelectOptions{
InterruptCh: ctx.InterruptCh,
NodeID: ctx.ExecutionOptions.NodeID,
MaxSeriesN: e.MaxSelectSeriesN,
}
// Replace instances of "now()" with the current time, and check the resultant times.
nowValuer := influxql.NowValuer{Now: now}
stmt.Condition = influxql.Reduce(stmt.Condition, &nowValuer)
// Replace instances of "now()" with the current time in the dimensions.
for _, d := range stmt.Dimensions {
d.Expr = influxql.Reduce(d.Expr, &nowValuer)
}
var err error
opt.MinTime, opt.MaxTime, err = influxql.TimeRange(stmt.Condition)
if err != nil {
return nil, stmt, err
}
if opt.MaxTime.IsZero() {
// In the case that we're executing a meta query where the user cannot
// specify a time condition, then we expand the default max time
// to the maximum possible value, to ensure that data where all points
// are in the future are returned.
if influxql.Sources(stmt.Sources).HasSystemSource() {
opt.MaxTime = time.Unix(0, influxql.MaxTime).UTC()
} else {
if interval, err := stmt.GroupByInterval(); err != nil {
return nil, stmt, err
} else if interval > 0 {
opt.MaxTime = now
} else {
opt.MaxTime = time.Unix(0, influxql.MaxTime).UTC()
}
}
}
if opt.MinTime.IsZero() {
opt.MinTime = time.Unix(0, influxql.MinTime).UTC()
}
// Convert DISTINCT into a call.
stmt.RewriteDistinct()
// Remove "time" from fields list.
stmt.RewriteTimeFields()
// Rewrite any regex conditions that could make use of the index.
stmt.RewriteRegexConditions()
// Create an iterator creator based on the shards in the cluster.
ic, err := e.iteratorCreator(stmt, &opt)
if err != nil {
return nil, stmt, err
}
// Expand regex sources to their actual source names.
if stmt.Sources.HasRegex() {
sources, err := ic.ExpandSources(stmt.Sources)
if err != nil {
return nil, stmt, err
}
stmt.Sources = sources
}
// Rewrite wildcards, if any exist.
tmp, err := stmt.RewriteFields(ic)
if err != nil {
return nil, stmt, err
}
stmt = tmp
if e.MaxSelectBucketsN > 0 && !stmt.IsRawQuery {
interval, err := stmt.GroupByInterval()
if err != nil {
return nil, stmt, err
}
if interval > 0 {
// Determine the start and end time matched to the interval (may not match the actual times).
min := opt.MinTime.Truncate(interval)
max := opt.MaxTime.Truncate(interval).Add(interval)
// Determine the number of buckets by finding the time span and dividing by the interval.
buckets := int64(max.Sub(min)) / int64(interval)
if int(buckets) > e.MaxSelectBucketsN {
return nil, stmt, fmt.Errorf("max-select-buckets limit exceeded: (%d/%d)", buckets, e.MaxSelectBucketsN)
}
}
}
// Create a set of iterators from a selection.
itrs, err := influxql.Select(stmt, ic, &opt)
if err != nil {
return nil, stmt, err
}
if e.MaxSelectPointN > 0 {
monitor := influxql.PointLimitMonitor(itrs, influxql.DefaultStatsInterval, e.MaxSelectPointN)
ctx.Query.Monitor(monitor)
}
return itrs, stmt, nil
}