Steps to Reindex Elasticsearch Data
For the demonstration, I am using elasticsearch v7.0.0.There are six stages to reindexing:In this blog, we would be reindexing a sample index called “companydatabase”.Step 1 : Get Index data
Get all existing index data and note down the docs count of the index which is going to reindex.curl -X GET \
'http://localhost:9200/_cat/indices/%2A?v=&s=index:desc' \
Step 2 : Create a New Index
Create a new index with newly updated mapping and versioning. We shall call it companydatabase_v2curl -X PUT \
http://localhost:9200/companydatabase_v2 \
-H 'Content-Type: application/json' \
-d '{
"mappings": {
"properties": {
"FirstName": {
"type": "text"
},
"Gender": {
"type": "text"
},
"LastName": {
"type": "text"
},
"Salary": {
"type": "text"
}
}
}
}'
Step 3 : Transfer data of old index into the new
Now we shall transfer data of old index into the newly created index with _reindex command. In our case, we are transferring data from companydatabase to companydatabase_v2curl -X POST \
http://localhost:9200/_reindex \
-H 'Content-Type: application/json' \
-d '{
"source": {
"index": "companydatabase"
},
"dest": {
"index": "companydatabase_v2"
}
}'
Step 4 : Verify newly created index
Always double-check that the newly created index should have the exact number of documents of the old index. We have 50,000 documents in our old index companydatabase which are copied to the newly created index companydatabase_v2.Confirm newly created index has an equal number of documents with the old index using the curl request shown below.curl -X GET \
'http://localhost:9200/companydatabase_v2/_search?scroll=10m&size=50' \
-H 'Content-Type: application/json' \
-d '{
"query" : {
"match_all" : {}
}
}'Step 5 : Delete Older Index
Once it is confirmed that all both the index has equal number of documents, it is safe to delete older index.curl -X DELETE \
http://localhost:9200/companydatabase
Final Step
We are in the final step and we need to do a couple of things here so I am going to break it down into sub steps.We have to create an alias with the name of the old index for newly created index In our case, we have an old index called companydatabase which was deleted in the previous step.Step 6.1Check if alias of that name already exists if you have created before. If exists then we’ve to delete that alias before created new alias.curl -X POST \
http://localhost:9200/_aliases \
-d '{
"actions": [
{
"remove": {
"index": "companydatabase_v2",
"alias": "companydatabase"
}
}
]
}'curl -X POST \
http://localhost:9200/_aliases \
-H 'Content-Type: application/json' \
-d '{
"actions": [
{
"add": {
"index": "companydatabase_v2",
"alias": "companydatabase"
}
}
]
}'
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