ppl-reference

name	ppl-reference
description	Comprehensive PPL (Piped Processing Language) reference for OpenSearch with command syntax, functions, and examples for observability queries.

PPL Language Reference

Piped Processing Language (PPL) for OpenSearch. Queries use pipe-delimited syntax starting with source=<index> and chaining commands with |. Grammar source: https://github.com/opensearch-project/sql

Field Name Escaping

Field names containing dots, @, or other special characters must be enclosed in backticks:

`attributes.gen_ai.operation.name`, `attributes.gen_ai.usage.input_tokens`, `status.code`, `events.attributes.exception.type`, `@timestamp`

Critical for OTel attribute fields which use dotted naming conventions.

API Endpoints

POST /_plugins/_ppl              # Execute query
POST /_plugins/_ppl/_explain     # Get execution plan

Body: {"query": "<ppl_query>"}

---

Commands

Core

source=<index-pattern> — Start a query. Alias: search source=.

source=otel-v1-apm-span-* | head 10

where <condition> — Filter results. Operators: =, !=, <, >, <=, >=, AND, OR, NOT, LIKE, IN, BETWEEN, IS NULL, IS NOT NULL.

source=otel-v1-apm-span-* | where `status.code` = 2 | head 10

fields [+|-] <field-list> — Select (+) or exclude (-) fields. Default is +.

source=otel-v1-apm-span-* | fields traceId, spanId, serviceName, durationInNanos | head 10

stats <aggregation>... [by <field-list>] — Aggregate. Functions: count(), sum(), avg(), max(), min(), var_samp(), var_pop(), stddev_samp(), stddev_pop(), distinct_count(), percentile(field, pct), earliest(), latest(), list(), values(), first(), last().

source=otel-v1-apm-span-* | stats count() as span_count, avg(durationInNanos) as avg_duration by serviceName

sort [+|-] <field> — + ascending (default), - descending.

source=otel-v1-apm-span-* | sort - durationInNanos | head 10

head [N] — Limit (default N=10).

source=otel-v1-apm-span-* | head 5

eval <field> = <expression> — Compute new fields.

source=otel-v1-apm-span-* | eval duration_ms = durationInNanos / 1000000 | fields traceId, serviceName, duration_ms | sort - duration_ms | head 10

dedup [N] <field-list> [keepempty=<bool>] [consecutive=<bool>] — Remove duplicates.

Caveat: dedup may throw a ClassCastException on fields with mixed types. Ensure consistent type.

source=otel-v1-apm-span-* | dedup serviceName | fields serviceName

rename <old> AS <new> — Rename fields.

source=otel-v1-apm-span-* | rename serviceName as service, durationInNanos as duration | fields traceId, service, duration | head 10

top [N] <field> [by <group>] — Most frequent values.

source=otel-v1-apm-span-* | top 5 serviceName

rare <field> [by <group>] — Least frequent values.

source=otel-v1-apm-span-* | rare `attributes.gen_ai.operation.name`

table <field-list> — Tabular display (alias for fields in some contexts).

source=otel-v1-apm-span-* | where `status.code` = 2 | table traceId, spanId, serviceName, name | head 10

reverse — Reverse the order of results.

source=otel-v1-apm-span-* | sort startTime | head 20 | reverse

Time-Series

timechart span=<interval> <aggregation>... [by <field>] — Time-bucketed aggregation. Rate functions: per_second(), per_minute(), per_hour(), per_day().

source=otel-v1-apm-span-* | timechart span=5m count() as span_count by serviceName
source=otel-v1-apm-span-* | timechart span=1h per_minute(count()) as spans_per_min by serviceName

chart <aggregation>... by <field> — General charting.

source=otel-v1-apm-span-* | chart avg(durationInNanos) by serviceName

bin / span(<field>, <interval>) — Bucket values. See Span Expression section below.

source=otel-v1-apm-span-* | stats count() by span(durationInNanos, 1000000000)

trendline [sort <field>] sma(<period>, <field>) [as <alias>] — Simple moving average.

source=otel-v1-apm-span-* | trendline sort startTime sma(10, durationInNanos) as avg_duration | fields startTime, durationInNanos, avg_duration | head 50

streamstats <aggregation>... [by <field>] — Running cumulative stats.

Caveat: Processes all rows in memory. Always add | head N before streamstats to limit data volume.

source=otel-v1-apm-span-* | sort startTime | head 50 | streamstats count() as running_count, sum(`attributes.gen_ai.usage.input_tokens`) as cumulative_tokens | fields startTime, running_count, cumulative_tokens

eventstats <aggregation>... [by <field>] — Add aggregation as new field without collapsing rows.

Caveat: Processes all rows in memory. Always add | head N before eventstats.

source=otel-v1-apm-span-* | head 100 | eventstats avg(durationInNanos) as avg_svc_duration by serviceName | eval deviation = durationInNanos - avg_svc_duration | fields traceId, serviceName, durationInNanos, avg_svc_duration, deviation | sort - deviation | head 20

Parse / Extract

parse <field> '<regex-with-named-groups>' — Extract fields via regex.

Caveat: May silently drop extracted fields on some OpenSearch versions. Use grok or rex if parse misbehaves.

source=logs-otel-v1-* | parse body '(?P<level>\w+): (?P<msg>.+)' | fields level, msg | head 10

grok <field> '<grok-pattern>' — Extract via named Grok patterns.

Caveat: Processes all rows in memory. Always add | head N before grok.

source=logs-otel-v1-* | head 100 | grok body '%{LOGLEVEL:level} %{GREEDYDATA:message}' | fields level, message | head 10

rex field=<field> '<regex>' — Splunk-compatible regex extract.

source=logs-otel-v1-* | rex field=body '(?<statuscode>\d{3})' | fields statuscode, body | head 10

regex — Filter results using a regular expression match on a field (used within where).

source=logs-otel-v1-* | where body like '%error%' | fields traceId, body, severityText | head 10

patterns <field> — Auto-cluster similar log messages.

source=logs-otel-v1-* | patterns body | fields body, patterns_field | head 20

spath input=<field> [path=<path>] [output=<field>] — Extract from structured data (JSON/XML).

Note: Verify the target field exists (describe <index>) before using spath.

source=otel-v1-apm-span-* | where isnotnull(`attributes.gen_ai.tool.name`) | spath input=`attributes.gen_ai.tool.name` | head 10

Join / Lookup / Subquery

join left=<alias> right=<alias> ON <condition> <right-source> — Types: inner, left, right, cross.

source=otel-v1-apm-span-* | join left=s right=l ON s.traceId = l.traceId logs-otel-v1-* | fields s.spanId, s.name, l.severityText, l.body | head 10

lookup <lookup-index> <match-field> [AS <alias>] [OUTPUT <field-list>] — Enrich from another index.

Note: The service map index (otel-v2-apm-service-map) uses sourceNode/targetNode, not serviceName.

source=otel-v1-apm-span-* | lookup otel-v2-apm-service-map serviceName AS `sourceNode` | fields serviceName, `targetNode`, durationInNanos | head 10

graphlookup <index> connectFromField=<f> connectToField=<f> [maxDepth=<N>] — Graph traversal.

Caveat: Limited support in OpenSearch 3.x PPL. Test before relying on this.

source=otel-v2-apm-service-map | graphlookup otel-v2-apm-service-map connectFromField=`destination.domain` connectToField=serviceName maxDepth=3 as dependencies | head 10

where <field> IN [ source=<index> | ... | fields <field> ] — Subquery filter.

source=otel-v1-apm-span-* | where traceId IN [ source=otel-v1-apm-span-* | where `status.code` = 2 | fields traceId ] | fields traceId, spanId, serviceName, name | head 20

append [ source=<index> | ... ] — Append rows from another query.

source=otel-v1-apm-span-* | stats count() as cnt by serviceName | append [ source=logs-otel-v1-* | stats count() as cnt by `resource.attributes.service.name` ] | head 20

appendcol [ <commands> ] — Append columns from a sub-pipeline.

Caveat: source= is NOT valid inside appendcol[] — it operates on the current result set. Use append if you need data from another index.

source=otel-v1-apm-span-* | stats count() as span_count, avg(durationInNanos) as avg_dur | appendcol [ stats max(durationInNanos) as max_dur ]

appendpipe [ <commands> ] — Append results of sub-pipeline on current data.

source=otel-v1-apm-span-* | stats count() as cnt by serviceName | appendpipe [ stats sum(cnt) as total ]

Transform

fillnull [with <value>] [<field-list>] — Replace nulls.

Caveat: Backtick-quoted field names are NOT supported in fillnull field list. Use eval to rename dotted fields first, or apply without a field list.

source=otel-v1-apm-span-* | eval tokens = `attributes.gen_ai.usage.input_tokens` | fillnull with 0 tokens

flatten <field> — Flatten nested fields to top level.

source=otel-v1-apm-span-* | flatten events | head 10

expand <field> / mvexpand <field> — Expand array/multi-value fields into separate rows.

source=otel-v1-apm-span-* | expand events | fields traceId, spanId, events | head 20
source=otel-v1-apm-span-* | mvexpand events | fields traceId, spanId, events | head 20

transpose [<N>] — Pivot rows into columns.

source=otel-v1-apm-span-* | stats count() as cnt by serviceName | transpose

mvcombine <field> — Combine rows with same key into multi-value field.

source=otel-v1-apm-span-* | fields traceId, serviceName | mvcombine serviceName | head 10

nomv <field> — Multi-value → single-value.

Caveat: Only works on string arrays. Use flatten or expand for nested object arrays.

source=otel-v1-apm-span-* | nomv events | fields traceId, events | head 10

convert <function>(<field>) [as <alias>] — Type conversion. Functions: auto(), num(), ip(), ctime(), dur2sec(), mktime(), mstime(), rmcomma(), rmunit(), memk(), none().

source=otel-v1-apm-span-* | eval duration_str = CAST(durationInNanos AS STRING) | convert num(duration_str) as duration_num | fields traceId, duration_num | head 10

eval <field> = replace(<field>, '<old>', '<new>') — Replace values via replace() string function.

source=logs-otel-v1-* | eval severityText = replace(severityText, 'ERROR', 'ERR') | fields severityText, body | head 10

Totals

addcoltotals [<field-list>] — Add summary row with column totals.

source=otel-v1-apm-span-* | stats count() as cnt by serviceName | addcoltotals

addtotals [row=<bool>] [col=<bool>] [<field-list>] — Add row with sum of numeric fields.

source=otel-v1-apm-span-* | stats sum(`attributes.gen_ai.usage.input_tokens`) as input_tok, sum(`attributes.gen_ai.usage.output_tokens`) as output_tok by serviceName | addtotals

ML

ad [time_field=<field>] [number_of_trees=<N>] [shingle_size=<N>] [time_zone=<tz>] — Anomaly detection.

Note: ad takes no positional field argument; it auto-detects from preceding stats/eval output.

source=otel-v1-apm-span-* | where durationInNanos > 0 | ad time_field=startTime number_of_trees=100 time_zone="UTC" | head 50

kmeans [centroids=<N>] [iterations=<N>] [distance_type=<type>] — K-means clustering.

Note: No positional field args; operates on all numeric fields from preceding output. Use fields to control input.

source=otel-v1-apm-span-* | where durationInNanos > 0 | fields traceId, serviceName, durationInNanos | kmeans centroids=3 | fields traceId, serviceName, durationInNanos, ClusterID | head 30

ml action=<algorithm> — General ML command. Supported: kmeans, ad.

Note: ml action=rcf is NOT valid in OpenSearch 3.x. Use ad directly for Random Cut Forest.

source=otel-v1-apm-span-* | where durationInNanos > 0 | ml action=kmeans centroids=3 | head 50

System Commands

Caveat: describe and show datasources are standalone top-level commands, NOT pipe commands. They cannot appear after |.

• ✓ describe my-index-*
• ✗ source=my-index-* | describe

describe otel-v1-apm-span-*       # Inspect index mapping/field types
show datasources                   # List PPL data sources

Display

fieldformat <field> = <format-expr> — Format display without changing data.

source=otel-v1-apm-span-* | eval duration_ms = durationInNanos / 1000000 | fieldformat duration_ms = CONCAT(CAST(duration_ms AS STRING), ' ms') | fields traceId, serviceName, duration_ms | head 10

---

Span Expression

Buckets numeric or datetime values into intervals. Used with stats, timechart, chart.

Syntax: span(<field>, <interval>)

Time units: ms, s, m (minutes), h, d, w, M (months), q (quarters), y.

source=otel-v1-apm-span-* | stats count() as span_count, avg(durationInNanos) as avg_duration by span(startTime, 1h)
source=otel-v1-apm-span-* | stats count() by span(durationInNanos, 1000000000)   # numeric, plain number

---

Functions

Aggregation (for stats, eventstats, streamstats, timechart, chart)

Function	Description
count(), sum(f), avg(f), max(f), min(f)	Basic aggregations
var_samp(f), var_pop(f), stddev_samp(f), stddev_pop(f)	Variance/stddev
distinct_count(f)	Count distinct values
percentile(f, pct)	Value at percentile
earliest(f), latest(f)	Chronological first/last
first(f), last(f)	Result-order first/last
list(f), values(f)	All / distinct values as list
covar_pop(f1, f2), covar_samp(f1, f2)	Covariance

source=otel-v1-apm-span-* | stats count() as total, avg(durationInNanos) as avg_ns, percentile(durationInNanos, 95) as p95_ns, distinct_count(serviceName) as services

Note: corr() is NOT supported in OpenSearch 3.x PPL. Use covar_samp with separate stddev calls to approximate Pearson correlation.

source=otel-v1-apm-span-* | where `attributes.gen_ai.usage.input_tokens` > 0 | stats covar_samp(`attributes.gen_ai.usage.input_tokens`, durationInNanos) as token_duration_covar

Condition

Function	Description
isnull(f), isnotnull(f)	Null check
if(cond, true_val, false_val)	Conditional
ifnull(f, default), nullif(a, b), coalesce(v1, v2, ...)	Null handling
case(cond1, val1, cond2, val2, ..., else_val)	Multi-branch
field LIKE 'pattern', field IN (v1, ...), field BETWEEN a AND b	Used in where

source=otel-v1-apm-span-* | eval status_label = case(`status.code` = 0, 'UNSET', `status.code` = 1, 'OK', `status.code` = 2, 'ERROR') | stats count() by status_label

Conversion

Function	Description
cast(f AS type)	Cast (STRING, INT, LONG, FLOAT, DOUBLE, BOOLEAN, DATE, TIMESTAMP)
tostring(f), tonumber(f), toint(f), tolong(f), tofloat(f), todouble(f), toboolean(f)	Type shortcuts

source=otel-v1-apm-span-* | eval duration_ms = CAST(durationInNanos AS DOUBLE) / 1000000.0 | fields traceId, serviceName, duration_ms | sort - duration_ms | head 10

Datetime

Function	Description
now(), curdate(), curtime(), sysdate()	Current time
utc_date(), utc_time(), utc_timestamp()	UTC variants
date_format(date, fmt)	Format (%Y-%m-%d %H:%i:%s)
date_add(d, INTERVAL n unit), date_sub(d, INTERVAL n unit), adddate, subdate	Add/subtract
datediff(d1, d2)	Days between
timestampadd(unit, n, ts), timestampdiff(unit, t1, t2)	Precise delta
day(), month(), year(), hour(), minute(), second()	Extract components
dayofweek(), dayofyear(), week()	Calendar components
unix_timestamp(d), from_unixtime(epoch)	Epoch conversion
maketime(h, m, s), makedate(year, doy)	Construct
period_add(p, n), period_diff(p1, p2)	YYMM/YYYYMM arithmetic

source=otel-v1-apm-span-* | where startTime > DATE_SUB(NOW(), INTERVAL 1 HOUR) | stats count() as recent_spans by serviceName

String

Function	Description
concat(...), length(s), char_length(s), octet_length(s), bit_length(s)	Basic
lower(s), upper(s), reverse(s)	Case / reverse
trim(s), ltrim(s), rtrim(s)	Trim
substring(s, start [, len]), substr, mid, left(s, n), right(s, n)	Substring
replace(s, from, to), regexp_replace(s, pattern, repl)	Replace
locate(sub, s [, pos]), position(sub IN s), instr(s, sub)	Search
lpad(s, len, pad), rpad(s, len, pad), space(n), repeat(s, n)	Padding
strcmp(a, b), ascii(s), format(val, decimals)	Misc
regexp(s, pat), regexp_extract(s, pat [, group])	Regex (returns 0/1 or group)
field(s, v1, ...), find_in_set(s, list)	Position in list
insert(s, pos, len, new)	Insert

source=logs-otel-v1-* | eval body_lower = lower(body) | where body_lower like '%exception%' | eval short_body = left(body, 200) | fields traceId, severityText, short_body | head 10

Math

Function	Description
abs, ceil, floor, round(v [, dec]), truncate(v, dec), sign	Rounding / sign
sqrt, pow(b, e), exp, ln, log, log2, log10	Power / log
mod(a, b), conv(v, from, to), crc32	Misc
sin, cos, tan, asin, acos, atan, atan2(y, x), cot	Trig
degrees(r), radians(d), pi(), e(), rand([seed])	Constants / conversion

source=otel-v1-apm-span-* | eval duration_ms = round(durationInNanos / 1000000.0, 2) | where duration_ms > 0 | fields traceId, serviceName, duration_ms | sort - duration_ms | head 10

Collection / Multi-Value

Function	Description
array(v1, v2, ...), split(f, delim)	Construct
mvcount(f), mvindex(f, i), mvfirst(f), mvlast(f)	Access
mvappend(f1, f2), mvjoin(f, delim), mvzip(f1, f2, delim)	Combine
mvdedup(f), mvsort(f), mvfilter(expr)	Transform
mvrange(start, end, step)	Generate

source=otel-v1-apm-span-* | eval tokens = array(`attributes.gen_ai.usage.input_tokens`, `attributes.gen_ai.usage.output_tokens`) | fields traceId, tokens | head 10

JSON

Function	Description
json_extract(f, path), json_extract_path_text(f, path)	Extract
json_keys(f), json_valid(f), json_array_length(f)	Inspect
json_array(v1, ...), json_object(k1, v1, ...), to_json_string(f)	Construct

source=otel-v1-apm-span-* | where json_valid(`attributes.gen_ai.tool.call.arguments`) | eval tool_args = json_extract(`attributes.gen_ai.tool.call.arguments`, '$') | fields traceId, `attributes.gen_ai.tool.name`, tool_args | head 10

Crypto / IP / System

Function	Description
md5(f), sha1(f), sha2(f, numBits)	Hash (numBits: 224/256/384/512)
cidrmatch(ip, 'cidr')	CIDR range check
geoip(ip)	Geo lookup (country, region, city, lat/lon)
typeof(f)	Data type of value

source=otel-v1-apm-span-* | eval trace_hash = md5(traceId) | fields traceId, trace_hash | head 5
source=otel-v1-apm-span-* | eval type_of_duration = typeof(durationInNanos) | fields traceId, durationInNanos, type_of_duration | head 5

Relevance (Full-Text Search)

Function	Description
match(field, query), match_query(...)	Full-text match
match_phrase(field, phrase), match_phrase_prefix(...), match_bool_prefix(...)	Phrase / prefix
multi_match([f1, f2], q)	Multi-field match
query_string([f1, f2], q), simple_query_string(...)	Lucene/simplified query syntax
wildcard_query(f, pattern)	* and ? wildcards
highlight(f), score(rf), scorequery(rf)	Highlighting / scoring

source=logs-otel-v1-* | where match(body, 'timeout error') | fields traceId, severityText, body | head 10

Expressions / Operators

• Arithmetic: +, -, *, /
• Comparison: =, != or <>, <, >, <=, >=
• Logical: AND, OR, NOT, XOR

source=otel-v1-apm-span-* | eval duration_ms = durationInNanos / 1000000, total_tokens = `attributes.gen_ai.usage.input_tokens` + `attributes.gen_ai.usage.output_tokens` | where duration_ms > 1000 AND total_tokens > 0 | fields traceId, serviceName, duration_ms, total_tokens | head 10

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References

• Official PPL docs — Fetch if queries fail due to OpenSearch version differences or new syntax.