Invoke convertToCapped and convert an existing collection to capped in MongoDB

MongoDBDatabaseBig Data Analytics

To convert an existing collection to capped, use convertToCapped. Let us create a collection with documents −

> db.demo260.insertOne({"Name":"Chris"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e47b1181627c0c63e7dba9b")
}
> db.demo260.insertOne({"Name":"Bob"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e47b11c1627c0c63e7dba9c")
}
> db.demo260.insertOne({"Name":"David"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e47b11f1627c0c63e7dba9d")
}

Display all documents from a collection with the help of find() method −

> db.demo260.find();

This will produce the following output −

{ "_id" : ObjectId("5e47b1181627c0c63e7dba9b"), "Name" : "Chris" }
{ "_id" : ObjectId("5e47b11c1627c0c63e7dba9c"), "Name" : "Bob" }
{ "_id" : ObjectId("5e47b11f1627c0c63e7dba9d"), "Name" : "David" }

Following is the query to invoke convertToCapped −

> db.runCommand( { convertToCapped: 'demo260', size: 8345 } );
{ "ok" : 1 }

Here is the query to check stats():

> db.demo260.stats()

This will produce the following output −

{
   "ns" : "test.demo260",
   "size" : 112,
   "count" : 3,
   "avgObjSize" : 37,
   "storageSize" : 16384,
   "capped" : true,
   "max" : -1,
   "maxSize" : 8448,
   "sleepCount" : 0,
   "sleepMS" : 0,
   "wiredTiger" : {
      "metadata" : {
         "formatVersion" : 1
      },
      "creationString" : "access_pattern_hint=none,allocation_size=4KB,app_metadata=(formatVersion=1),assert=(commit_timestamp=none,read_timestamp=none),block_allocation=best,block_compressor=snappy,cache_resident=false,checksum=on,colgroups=,collator=,columns=,dictionary=0,encryption=(keyid=,name=),exclusive=false,extractor=,format=btree,huffman_key=,huffman_value=,ignore_in_memory_cache_size=false,immutable=false,internal_item_max=0,internal_key_max=0,internal_key_truncate=true,internal_page_max=4KB,key_format=q,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=32KB,leaf_value_max=64MB,log=(enabled=true),lsm=(auto_throttle=true,bloom=true,bloom_bit_count=16,bloom_config=,bloom_hash_count=8,bloom_oldest=false,chunk_count_limit=0,chunk_max=5GB,chunk_size=10MB,merge_custom=(prefix=,start_generation=0,suffix=),merge_max=15,merge_min=0),memory_page_image_max=0,memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=false,prefix_compression_min=4,source=,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,type=file,value_format=u",
"type" : "file",
"uri" : "statistics:table:collection-61--7930664661263858819",
      "LSM" : {
         "bloom filter false positives" : 0,
         "bloom filter hits" : 0,
         "bloom filter misses" : 0,
         "bloom filter pages evicted from cache" : 0,
         "bloom filter pages read into cache" : 0,
         "bloom filters in the LSM tree" : 0,
         "chunks in the LSM tree" : 0,
         "highest merge generation in the LSM tree" : 0,
         "queries that could have benefited from a Bloom filter that did not exist" : 0,
         "sleep for LSM checkpoint throttle" : 0,
         "sleep for LSM merge throttle" : 0,
         "total size of bloom filters" : 0
      },
      "block-manager" : {
         "allocations requiring file extension" : 3,
         "blocks allocated" : 3,
         "blocks freed" : 0,
         "checkpoint size" : 4096,
         "file allocation unit size" : 4096,
         "file bytes available for reuse" : 0,
         "file magic number" : 120897,
         "file major version number" : 1,
         "file size in bytes" : 16384,
         "minor version number" : 0
      },
      "btree" : {
         "btree checkpoint generation" : 0,
         "column-store fixed-size leaf pages" : 0,
         "column-store internal pages" : 0,
         "column-store variable-size RLE encoded values" : 0,
         "column-store variable-size deleted values" : 0,
         "column-store variable-size leaf pages" : 0,
         "fixed-record size" : 0,
         "maximum internal page key size" : 368,
         "maximum internal page size" : 4096,
         "maximum leaf page key size" : 2867,
         "maximum leaf page size" : 32768,
         "maximum leaf page value size" : 67108864,
         "maximum tree depth" : 0,
         "number of key/value pairs" : 0,
         "overflow pages" : 0,
         "pages rewritten by compaction" : 0,
         "row-store internal pages" : 0,
         "row-store leaf pages" : 0
      },
      "cache" : {
         "bytes currently in the cache" : 514,
         "bytes dirty in the cache cumulative" : 0,
         "bytes read into cache" : 212,
         "bytes written from cache" : 212,
         "checkpoint blocked page eviction" : 0,
         "data source pages selected for eviction unable to be evicted" : 0,
         "eviction walk passes of a file" : 0,
         "eviction walk target pages histogram - 0-9" : 0,
         "eviction walk target pages histogram - 10-31" : 0,
         "eviction walk target pages histogram - 128 and higher" : 0,
         "eviction walk target pages histogram - 32-63" : 0,
         "eviction walk target pages histogram - 64-128" : 0,
         "eviction walks abandoned" : 0,
         "eviction walks gave up because they restarted their walk twice" : 0,
         "eviction walks gave up because they saw too many pages and found no candidates" : 0,
         "eviction walks gave up because they saw too many pages and found too few candidates" : 0,
         "eviction walks reached end of tree" : 0,
         "eviction walks started from root of tree" : 0,
         "eviction walks started from saved location in tree" : 0,
         "hazard pointer blocked page eviction" : 0,
         "in-memory page passed criteria to be split" : 0,
         "in-memory page splits" : 0,
         "internal pages evicted" : 0,
         "internal pages split during eviction" : 0,
         "leaf pages split during eviction" : 0,
         "modified pages evicted" : 2,
         "overflow pages read into cache" : 0,
         "page split during eviction deepened the tree" : 0,
         "page written requiring cache overflow records" : 0,
         "pages read into cache" : 2,
         "pages read into cache after truncate" : 1,
         "pages read into cache after truncate in prepare state" : 0,
         "pages read into cache requiring cache overflow entries" : 0,
         "pages requested from the cache" : 4,
         "pages seen by eviction walk" : 0,
         "pages written from cache" : 2,
         "pages written requiring in-memory restoration" : 0,
         "tracked dirty bytes in the cache" : 0,
         "unmodified pages evicted" : 0
      },
      "cache_walk" : {
         "Average difference between current eviction generation when the page was last considered" : 0,
         "Average on-disk page image size seen" : 0,
         "Average time in cache for pages that have been visited by the eviction server" : 0,
         "Average time in cache for pages that have not been visited by the eviction server" : 0,
         "Clean pages currently in cache" : 0,
         "Current eviction generation" : 0,
         "Dirty pages currently in cache" : 0,
         "Entries in the root page" : 0,
         "Internal pages currently in cache" : 0,
         "Leaf pages currently in cache" : 0,
         "Maximum difference between current eviction generation when the page was last considered" : 0,
         "Maximum page size seen" : 0,
         "Minimum on-disk page image size seen" : 0,
         "Number of pages never visited by eviction server" : 0,
         "On-disk page image sizes smaller than a single allocation unit" : 0,
         "Pages created in memory and never written" : 0,
         "Pages currently queued for eviction" : 0,
         "Pages that could not be queued for eviction" : 0,
         "Refs skipped during cache traversal" : 0,
         "Size of the root page" : 0,
         "Total number of pages currently in cache" : 0
      },
      "compression" : {
         "compressed pages read" : 0,
         "compressed pages written" : 0,
         "page written failed to compress" : 0,
         "page written was too small to compress" : 2,
         "raw compression call failed, additional data available" : 0,
         "raw compression call failed, no additional data available" : 0,
         "raw compression call succeeded" : 0
      },
      "cursor" : {
         "bulk-loaded cursor-insert calls" : 0,
         "close calls that result in cache" : 0,
         "create calls" : 2,
         "cursor operation restarted" : 0,
         "cursor-insert key and value bytes inserted" : 115,
         "cursor-remove key bytes removed" : 0,
         "cursor-update value bytes updated" : 0,
         "cursors reused from cache" : 0,
         "insert calls" : 3,
         "modify calls" : 0,
         "next calls" : 0,
         "prev calls" : 2,
         "remove calls" : 0,
         "reserve calls" : 0,
         "reset calls" : 7,
         "search calls" : 0,
         "search near calls" : 0,
         "truncate calls" : 0,
         "update calls" : 0
      },
      "reconciliation" : {
         "dictionary matches" : 0,
         "fast-path pages deleted" : 0,
         "internal page key bytes discarded using suffix compression" : 0,
         "internal page multi-block writes" : 0,
         "internal-page overflow keys" : 0,
         "leaf page key bytes discarded using prefix compression" : 0,
         "leaf page multi-block writes" : 0,
         "leaf-page overflow keys" : 0,
         "maximum blocks required for a page" : 0,
         "overflow values written" : 0,
         "page checksum matches" : 0,
         "page reconciliation calls" : 2,
         "page reconciliation calls for eviction" : 2,
         "pages deleted" : 0
      },
      "session" : {
         "cached cursor count" : 1,
         "object compaction" : 0,
         "open cursor count" : 0
      },
      "transaction" : {
         "update conflicts" : 0
      }
   },
   "nindexes" : 1,
   "totalIndexSize" : 16384,
   "indexSizes" : {
      "_id_" : 16384
   },
   "ok" : 1
}
raja
Published on 31-Mar-2020 08:29:08
Advertisements