Marklogic分片场景下cts:value-co-occurrences()索引延迟与结果异常排查

Hey there, let's tackle your issues step by step—you're running into empty results from cts:value-co-occurrences() after bulk loading data in a sharded MarkLogic setup, plus you need to track index latency and get visibility into per-shard index details. Here's what you can do:

一、追踪分片场景下的索引耗时 #

MarkLogic handles indexing across shards in a distributed way, so you'll need to check both global and per-node metrics to pinpoint latency:

1. Admin UI Monitoring Dashboard #

• Log into the Admin UI, navigate to Groups > [Your Group] > Databases > [Target DB] > Monitoring
• Switch to the Indexes tab to see global index build progress, completed task durations, and pending index work
• For per-shard visibility, head to the Hosts tab and look at the Indexer process metrics (CPU, memory) plus Pending Index Tasks—this will show you if a specific shard is falling behind on indexing

2. Built-in XQuery Monitoring Functions #

Run these in Query Console to get granular per-shard index task details:
First, pull indexer settings for your database:

xquery version "1.0-ml";
import module namespace admin = "http://marklogic.com/xdmp/admin" at "/MarkLogic/admin.xqy";

let $config := admin:get-configuration()
let $db-id := xdmp:database("[Your Database Name]")
return admin:database-get-indexer-settings($config, $db-id)

Then, check indexer status on every host (shard node):

for $host in xdmp:hosts()
return xdmp:host-status($host)/indexer

Look for elapsed-time and pending-tasks fields—these will tell you exactly how long index tasks are taking and if there's a backlog.

3. Node-Level Error Logs #

Each shard node's ErrorLog.txt (default path: [MarkLogic Install Dir]/Data/Logs) logs index task start/finish events. Search for keywords like Indexer or index task to find entries like this:

2024-05-20 14:30:00.123 Info: Indexer: Finished building element range index {http://example.com}name in 12000ms
These entries give you precise timestamps to calculate index build durations per shard.

二、查看分片级索引信息 #

The Admin UI shows global index config by default, but you can get per-shard index status with these methods:

1. Query Per-Forest (Shard) Index Status #

Run this XQuery to loop through each forest (each shard maps to one or more forests) and check its index build state:

xquery version "1.0-ml";
for $forest in xdmp:database-forests(xdmp:database("[Your Database Name]"))
let $forest-status := xdmp:forest-status($forest)
return (
  "Forest Name: " || xdmp:forest-name($forest),
  "Index Status:",
  $forest-status/indexes/range-indexes/range-index[
    element-name or path-expression
  ]/(element-name, path-expression, status, elapsed-time)
)

This returns whether each element/path range index on the shard is completed or in-progress, plus how long it took to build. If some shards have incomplete indexes, that's likely why cts:value-co-occurrences() is returning empty results—it's not seeing data from those shards.

2. Check Forest Sync Status #

In the Admin UI, go to Databases > [Target DB] > Forests and check the Status column for each forest. Ensure all are marked Open and no forests are stuck in Syncing mode. A syncing forest means its indexes aren't fully ready yet, so queries won't include its data.

3. Force a Shard Index Refresh #

If you find stale or incomplete indexes on a shard, manually clear and rebuild them (run during off-peak hours, as this is resource-heavy):
First, clear existing indexes for element/path ranges:

xquery version "1.0-ml";
for $forest in xdmp:database-forests(xdmp:database("[Your Database Name]"))
return xdmp:forest-clear-indexes($forest, (), "element-range-indexes", "path-range-indexes")

Then trigger a full database reindex:

xdmp:database-reindex(xdmp:database("[Your Database Name]"))

三、 Bonus: Troubleshoot Empty cts:value-co-occurrences() Results #

Beyond indexing issues, double-check these:

• Verify your cts:query filter is correctly targeting documents across all shards—watch out for namespace mismatches in element/path references
• Add the ("map") option to cts:value-co-occurrences() to get per-shard results, which lets you see exactly which shard isn't returning data:

cts:value-co-occurrences(
  cts:element-reference(xs:QName("your-target-element")),
  cts:element-reference(xs:QName("your-co-occurrence-element")),
  ("map")
)

If a shard's map entry is empty, you know that shard's indexes or data are the problem.

内容的提问来源于stack exchange，提问作者Navin Rawat