Filter vector matches

In Vector Search, you can restrict vector matching searches to a subset of the index by using Boolean rules. Boolean predicates tell Vector Search which vectors in the index to ignore. On this page you'll learn about how filtering works, see examples, and ways to efficiently query your data based on vector similarity.

With Vector Search you can restrict results by categorical and numeric restrictions. Adding restrictions, or "filtering" your index results are useful for multiple reasons, like the following examples:

• Improved result relevance: Vector Search is a powerful tool for finding semantically similar items. Filtering can be used to remove irrelevant results from the search results, such as items that are not in the correct language, category, price, or date range.

• Reduced number of results: Vector Search can return a large number of results, especially for large datasets. Filtering can be used to reduce the number of results to a more manageable number, while still returning the most relevant results.

• Segmented results: Filtering can be used to personalize the search results to the user's individual needs and preferences. For example, a user might want to filter the results to only include items that they have rated highly in the past or that fall into a specific price range.

Vector attributes

In a vector similarity search over a database of vectors, each vector is described by zero-or-more attributes. These attribute are known as tokens for token restricts and values for numeric restricts. These restricts can apply from each of several attribute categories, also known as namespaces.

In the following example application, vectors are tagged with a color, a price, and a shape:

• color, price, and shape are namespaces.
• red and blue are tokens from the color namespace.
• square and circle are tokens from the shape namespace.
• 100 and 50 are values from the price namespace.

Specify vector attributes

• To specify a "red circle": {color: red}, {shape: circle}.
• To specify a "red and blue square": {color: red, blue}, {shape: square}.
• To specify an object with no color, omit the "color" namespace in the restricts field.
• To specify numeric restricts for an object, note the namespace and the value in the appropriate field for the type. Int value should be specified in value_int, float value should be specified in value_float, and double value should be specified in value_double. Only one number type should be used for a given namespace.

For information about the schema used to specify this data, see Specify namespaces and tokens in the input data.

Queries

• Queries express an AND logical operator across namespaces and an OR logical operator within each namespace. A query that specifies {color: red, blue}, {shape: square, circle}, matches all database points that satisfy (red || blue) && (square || circle).
• A query that specifies {color: red}, matches all red objects of any kind, with no restriction on shape.
• Numeric restricts in queries require namespace, one of number values from value_int, value_float, and value_double, and operator op.
• Operator op is one of LESS, LESS_EQUAL, EQUAL, GREATER_EQUAL, and GREATER. For example, if the LESS_EQUAL operator is used, datapoints are eligible if their value is smaller or equal to the value used in the query.

The following code examples identify vector attributes in the sample application:

{
  namespace: "price"
  value_int: 20
  op: LESS
}

{
  namespace: "length"
  value_float: 0.3
  op: GREATER_EQUAL
}

{
  namespace: "width"
  value_double: 0.5
  op: EQUAL
}

Denylist

To enable more advanced scenarios, Google supports a form of negation known as denylist tokens. When a query denylists a token, matches are excluded for any datapoint that has the denylisted token. If a query namespace has only denylisted tokens, all points not explicitly denylisted, match, in exactly the same way that an empty namespace matches with all points.

Datapoints can also denylist a token, excluding matches with any query specifying that token.

For example, define the following data points with the specified tokens:

A: {}                  // empty set matches everything
B: {red}               // only a 'red' token
C: {blue}              // only a 'blue' token
D: {orange}            // only an 'orange' token
E: {red, blue}         // multiple tokens
F: {red, !blue}        // deny the 'blue' token
G: {red, blue, !blue}  // An unlikely edge-case
H: {!blue}             // deny-only (similar to empty-set)

The system behaves as follows:

• Empty query namespaces are match-all wildcards. For example, Q:{} matches DB:{color:red}.

• Empty datapoint namespaces are not match-all wildcards. For example, Q:{color:red} doesn't match DB:{}.

  

Specify namespaces and tokens or values in the input data

For information about how to structure your input data overall, see Input data format and structure.

The following tabs show how to specify the namespaces and tokens associated with each input vector.

JSON

• For each vector's record, add a field called restricts, to contain an array of objects, each of which is a namespace.

  • Each object must have a field named namespace. This field is the TokenNamespace.namespace, namespace.
  • The value of the field allow, if present, is an array of strings. This array of strings is the TokenNamespace.string_tokens list.
  • The value of the field deny, if present, is an array of strings. This array of strings is the TokenNamespace.string_denylist_tokens list.

The following are two example records in JSON format:

{"id": "42", "embedding": [0.5, 1.0], "restricts": [{"namespace": "class",
"allow": ["cat", "pet"]},{"namespace": "category", "allow": ["feline"]}]}
{"id": "43", "embedding": [0.6, 1.0], "restricts": [{"namespace":
"class", "allow": ["dog", "pet"]},{"namespace": "category", "allow":
["canine"]}]}

• For each vector's record, add a field called numeric_restricts, to contain an array of objects, each of which is a numeric restrict.

  • Each object must have a field named namespace. This field is the NumericRestrictNamespace.namespace, namespace.
  • Each object must have one of value_int, value_float, and value_double.
  • Each object must not have a field named op. This field is only for query.

The following are two example records in JSON format:

{"id": "42", "embedding": [0.5, 1.0], "numeric_restricts":
[{"namespace": "size", "value_int": 3},{"namespace": "ratio", "value_float": 0.1}]}
{"id": "43", "embedding": [0.6, 1.0], "numeric_restricts": [{"namespace":
"weight", "value_double": 0.3}]}

Avro

Avro records use the following schema:

{
  "type": "record",
  "name": "FeatureVector",
  "fields": [
    {
      "name": "id",
      "type": "string"
    },
    {
      "name": "embedding",
      "type": {
        "type": "array",
        "items": "float"
      }
    },
    {
      "name": "restricts",
      "type": [
        "null",
        {
          "type": "array",
          "items": {
            "type": "record",
            "name": "Restrict",
            "fields": [
              {
                "name": "namespace",
                "type": "string"
              },
              {
                "name": "allow",
                "type": [
                  "null",
                  {
                    "type": "array",
                    "items": "string"
                  }
                ]
              },
              {
                "name": "deny",
                "type": [
                  "null",
                  {
                    "type": "array",
                    "items": "string"
                  }
                ]
              }
            ]
          }
        }
      ]
    },
    {
      "name": "numeric_restricts",
      "type": [
        "null",
        {
          "type": "array",
          "items": {
            "name": "NumericRestrict",
            "type": "record",
            "fields": [
              {
                "name": "namespace",
                "type": "string"
              },
              {
                "name": "value_int",
                "type": [ "null", "int" ],
                "default": null
              },
              {
                "name": "value_float",
                "type": [ "null", "float" ],
                "default": null
              },
              {
                "name": "value_double",
                "type": [ "null", "double" ],
                "default": null
              }
            ]
          }
        }
      ],
      "default": null
    },
    {
      "name": "crowding_tag",
      "type": [
        "null",
        "string"
      ]
    }
  ]
}

CSV

• Token restricts

  • For each vector's record, add comma separated pairs of format name=value to specify token namespace restricts. The same name may be repeated if there are multiple values in a namespace.

    For example, color=red,color=blue represents this TokenNamespace:

    {
      "namespace": "color"
      "string_tokens": ["red", "blue"]
    }
    

  • For each vector's record, add comma separated pairs of format name=!value to specify excluded value for token namespace restricts.

    For example, color=!red represents this TokenNamespace:

    {
      "namespace": "color"
      "string_blacklist_tokens": ["red"]
    }
    

• Numeric restricts

  • For each vector's record, add comma separated pairs of format #name=numericValue with number type suffix to specify numeric namespace restricts.

    Number type suffix is i for int, f for float, and d for double. The same name shouldn't be repeated as there should be a single value associated per namespace.

    For example, #size=3i represents this NumericRestrictNamespace:

    {
      "namespace": "size"
      "value_int": 3
    }
    

    #ratio=0.1f represents this NumericRestrictNamespace:

    {
      "namespace": "ratio"
      "value_float": 0.1
    }
    

    #weight=0.3d represents this NumericRestriction:

    {
      "namespace": "weight"
      "value_double": 0.3
    }
    

What's next

• Learn how to query your indexes to find their nearest neighbors.
• Learn how to select, query, and display these metrics in Metrics Explorer.