CODEWITHSUNDEEP
firebasegoogle-cloud-firestore
Yuuta Moriyama
Yuuta Moriyama

Reputation: 459

firestore array-like data structure indexing limitation

In the firestore documentation, there is a description below

Indexing limits - A single document can have only 20,000 properties in order to use Cloud Firestore built-in indexes. If your array-like data structure grows to tens of thousands of members, you may run into this limit.

https://cloud.google.com/firestore/docs/solutions/arrays

I want to know how I can interpret the description. Which of two patterns meet the limitation?

<pattern 1: categories in one document above 20,000> 
    doc1
     - id:111  
     - categories: {aaaa:true, aaab:false, aaac:true, aaad: false, aaae:true, aaaf:true, aaag:true, aaah:true, aaai:true, aaaj:true, ,,,,,,,,,,, }

another pattern

<pattern 2:  categories in one document is a few but as a collection of document number of categories above 20,000> 
    doc_1
    - id:111
    categories{aaaa:true, aaab:false, aaac:true, only several element}
    doc_2
    - id:111
    categories{aaad:true, aaae:false, aaaf:true, only several element}
    doc_3
    - id:111
    categories{aaag:true, aaah:false, aaai:true, only several element}

I believe that pattern 1 reach the limit, but is pattern 2 reach the limit?

Upvotes: 3

Views: 636

Answers (1)

Sam Stern
Sam Stern

Reputation: 25134

The limit is on the total number of properties, so it's possible that both patterns could hit the 20,000 limit.

Here are some examples of counting properties that may help:

This document has two properties: a and b.c

{
  a: "foo",
  b: {
   c: "bar"
  }
}

This document has four properties: a, b, b.c, d

{
  a: "foo",
  b: {
   c: "bar",
  },
  d: ["quz", "qaz"]
}

And this document has four as well:

{
  a: "foo",
  b: {
   c: "bar",
  },
  d: ["quz", "qaz", "apple", "banana"]
}

This document has five:

{
  a: "foo",
  b: {
   c: "bar",
  },
  d: ["quz", "qaz"],
  e: ["apple", "banana"]
}

So it's not about the length of any single array or how deeply nested things are, it's about the total number of queryable values.

EDIT 03/05/18: I was wrong before when I said that array members counted separately against the index. They do not, that was something we had in place when Firestore was in Alpha that never applied in a public release.

Upvotes: 2

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