9.3. Compressed storage

This section explains Neo4j property value compression and disk usage.

Neo4j can in many cases compress and inline the storage of property values, such as short arrays and strings, with the purpose of saving disk space and possibly an I/O operation.

Compressed storage of short arrays

Neo4j will try to store your primitive arrays in a compressed way. To do that, it employs a "bit-shaving" algorithm that tries to reduce the number of bits required for storing the members of the array. In particular:

  1. For each member of the array, it determines the position of leftmost set bit.
  2. Determines the largest such position among all members of the array.
  3. It reduces all members to that number of bits.
  4. Stores those values, prefixed by a small header.

That means that when even a single negative value is included in the array then the original size of the primitives will be used.

There is a possibility that the result can be inlined in the property record if:

For example, an array long[] {0L, 1L, 2L, 4L} will be inlined, as the largest entry (4) will require 3 bits to store so the whole array will be stored in 4 × 3 = 12 bits. The array long[] {-1L, 1L, 2L, 4L} however will require the whole 64 bits for the -1 entry so it needs 64 × 4 = 32 bytes and it will end up in the dynamic store.

Compressed storage of short strings

Neo4j will try to classify your strings in a short string class and if it manages that it will treat it accordingly. In that case, it will be stored without indirection in the property store, inlining it instead in the property record, meaning that the dynamic string store will not be involved in storing that value, leading to reduced disk footprint. Additionally, when no string record is needed to store the property, it can be read and written in a single lookup, leading to performance improvements and less disk space required.

The various classes for short strings are:

In addition to the string’s contents, the number of characters also determines if the string can be inlined or not. Each class has its own character count limits, which are

Table 9.2. Character count limits
String class Character count limit

Numerical, Date and Hex


Uppercase, Lowercase and E-mail


URI, Alphanumerical and Alphasymbolical








That means that the largest inline-able string is 54 characters long and must be of the Numerical class and also that all Strings of size 14 or less will always be inlined.

Also note that the above limits are for the default 41 byte PropertyRecord layout — if that parameter is changed via editing the source and recompiling, the above have to be recalculated.