Enabling and Disabling Search Optimization

To enable search optimization, use a role that has the necessary privileges, then enable it for an entire table or specific columns using the ALTER TABLE … ADD SEARCH OPTIMIZATION command.

Required Access Control Privileges

To add, configure, or remove search optimization for a table, you must:

  • Have OWNERSHIP privilege on the table.

  • Have ADD SEARCH OPTIMIZATION privilege on the schema that contains the table. To grant this privilege:

    GRANT ADD SEARCH OPTIMIZATION ON SCHEMA <schema_name> TO ROLE <role>
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To use the search optimization service for a query, you just need the SELECT privilege on the table.

You do not need any additional privileges. Because SEARCH OPTIMIZATION is a table property, it is automatically detected and used (if appropriate) when querying a table.

Configuring Search Optimization

Note

Adding search optimization to a large table (a table containing terabytes (TB) or more of data) might result in an immediate increase in credit consumption over a short period of time.

When you add search optimization to a table, the maintenance service immediately starts building the search access paths for the table in the background. If the table is large, the maintenance service might massively parallelize this work, which can result in increased costs over a short period of time.

Before you add search optimization to a large table, get an estimate of these costs so that you know what to expect.

When you enable search optimization, you have a choice of enabling it for a whole table or for specific columns in the table.

  • Enabling search optimization for a whole table enables it for point-lookup queries on all eligible columns.

    To enable search optimization for a whole table, use the ALTER TABLE … ADD SEARCH OPTIMIZATION command without the ON clause.

  • Enabling search optimization for specific columns avoids spending credits on creating search access paths for columns that you do not often use in queries, and also allows you to select additional types of queries to be optimized for each column, potentially further increasing performance.

    To enable search optimization for specific columns, specifying the types of queries to be optimized, use the ON clause in the ALTER TABLE … ADD SEARCH OPTIMIZATION command. In the ON clause in ADD SEARCH OPTIMIZATION, you specify which columns should be enabled for search optimization. When enabling search optimization for a given column, you can also specify a search method (e.g. EQUALITY for equality and IN searches, GEO for GEOGRAPHY searches, or SUBSTRING for substring searches). You can enable more than one search method on the same column.

In general, enabling search optimization only for specific columns is the best practice.

The following sections explain how to configure search optimization for a table:

After you have configured search optimization, you can inspect your configuration to make sure it is correct.

You can remove search optimization from specific columns or whole tables when you have discovered that search optimization does not provide enough benefit.

Enabling Search Optimization for Specific Columns

To configure search optimization for a specific column, use the ALTER TABLE … ADD SEARCH OPTIMIZATION command with the ON clause.

Note

When running this command, use a role that has the privileges to add search optimization to the table.

The ON clause specifies that you want to configure search optimization for specific columns. For details on the syntax, see the section on ALTER TABLE … ADD SEARCH OPTIMIZATION.

Note

If you just want to apply search optimization for equality and IN predicates to all applicable columns in the table, see Enabling Search Optimization for an Entire Table.

After running this command, you can verify that the columns have been configured for search optimization.

The next sections contain examples that demonstrate how to specify the configuration for search optimization:

Example: Supporting Equality and IN Predicates for Specific Columns

To optimize searches with equality predicates for the columns c1, c2, and c3 in the table t1, execute the following statement:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(c1, c2, c3);
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You can also specify the same search method more than once in the ON clause:

-- This statement is equivalent to the previous statement.
ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(c1), EQUALITY(c2, c3);
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Example: Supporting Equality and IN Predicates for All Applicable Columns

To optimize searches with equality predicates for all applicable columns in the table, execute the following statement:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(*);
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Note the following:

Example: Supporting Different Types of Predicates

To optimize searches with equality predicates for the column c1 and c2 and substring searches for the column c3, execute the following statement:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(c1, c2), SUBSTRING(c3);
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Example: Supporting Different Predicates on the Same Column

To optimize searches for both equality predicates and substring predicates on the same column, c1, execute the following statement:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(c1), SUBSTRING(c1);
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Example: Supporting Equality and IN Predicates for a Field in a VARIANT

To optimize searches with equality predicates on the VARIANT field uuid nested in the field user in the VARIANT column c4, execute the following statement:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(c4:user.uuid);
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Example: Supporting Geospatial Functions

To optimize searches with predicates that use geospatial functions with GEOGRAPHY objects in the c1 column, execute the following statement:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON GEO(c1);
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Enabling Search Optimization for an Entire Table

To specify EQUALITY for all columns of the supported data types (except for VARIANT and GEOGRAPHY), use the ALTER TABLE … ADD SEARCH OPTIMIZATION command without the ON clause.

Note

When running this command, use a role that has the privileges to add search optimization to the table.

For example:

alter table test_table add search optimization;
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For more information on the syntax, see the section on search optimization in ALTER TABLE.

After running this command, you can verify that the columns have been configured for search optimization.

Effect on Subsequently Added Columns

After you run ALTER TABLE … ADD SEARCH OPTIMIZATION command without the ON clause, any columns that are subsequently added to the table will also be configured for optimization on EQUALITY.

However, if you execute ALTER TABLE … { ADD | DROP } SEARCH OPTIMIZATION with the ON clause on the same table, any columns that are subsequently added to the table will not be configured for EQUALITY automatically. You must execute ALTER TABLE … ADD SEARCH OPTIMIZATION ON … to configure these newly added columns for EQUALITY.

Verifying That a Table Is Configured For Search Optimization

To verify that the table and its columns have been configured for search optimization:

  1. Display the search optimization configuration for the table and its columns.

  2. Run the SHOW TABLES command to verify that search optimization has been added and to determine how much of the table has been optimized.

    For example:

    SHOW TABLES LIKE '%test_table%';
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    In the output from this command:

    • Verify that SEARCH_OPTIMIZATION is ON, which indicates that search optimization has been added.

    • Check the value of SEARCH_OPTIMIZATION_PROGRESS. This specifies the percentage of the table that has been optimized so far.

      When search optimization is first added to a table, the performance benefits do not appear immediately. The search optimization service starts populating data in the background. The benefits appear increasingly as the maintenance catches up to the current state of the table.

      Before you run a query to verify that search optimization is working, wait until this shows that the table has been fully optimized.

  3. Run a query to verify that search optimization is working.

    Note that the Snowflake optimizer automatically chooses when to use the search optimization service for a particular query. Users cannot control which queries search optimization is used for.

    Choose a query that the search optimization service is designed to optimize. See Identifying Queries That Can Benefit from Search Optimization.

  4. In the web UI, view the query plan for this query, and verify that the query node “Search Optimization Access” is part of the query plan.

Displaying the Search Optimization Configuration for a Table

To display the search optimization configuration for a table, use the DESCRIBE SEARCH OPTIMIZATION command.

For example, suppose that you execute the following statement to configure search optimization for a column:

ALTER TABLE t1 ADD SEARCH OPTIMIZATION ON EQUALITY(c1);
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Executing DESCRIBE SEARCH OPTIMIZATION produces the following output:

DESCRIBE SEARCH OPTIMIZATION ON t1;

+---------------+----------+--------+------------------+--------+
| expression_id |  method  | target | target_data_type | active |
+---------------+----------+--------+------------------+--------+
| 1             | EQUALITY | C1     | NUMBER(38,0)     | true   |
+---------------+----------+--------+------------------+--------+
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Removing Search Optimization From Specific Columns or the Entire Table

You can remove the search optimization configuration for specific columns, or you can remove the SEARCH OPTIMIZATION property from the entire table.

Dropping Search Optimization for Specific Columns

To drop the search optimization configuration for specific columns, use the following command: ALTER TABLE … DROP SEARCH OPTIMIZATION command with the ON clause.

For example, suppose that executing the DESCRIBE SEARCH OPTIMIZATION command prints the following expressions:

DESCRIBE SEARCH OPTIMIZATION ON t1;

+---------------+-----------+-----------+-------------------+--------+
| expression_id |  method   | target    | target_data_type  | active |
+---------------+-----------+-----------+-------------------+--------+
|             1 | EQUALITY  | C1        | NUMBER(38,0)      | true   |
|             2 | EQUALITY  | C2        | VARCHAR(16777216) | true   |
|             3 | EQUALITY  | C4        | NUMBER(38,0)      | true   |
|             4 | EQUALITY  | C5        | VARCHAR(16777216) | true   |
|             5 | EQUALITY  | V1        | VARIANT           | true   |
|             6 | SUBSTRING | C2        | VARCHAR(16777216) | true   |
|             7 | SUBSTRING | C5        | VARCHAR(16777216) | true   |
|             8 | GEO       | G1        | GEOGRAPHY         | true   |
|             9 | EQUALITY  | V1:"key1" | VARIANT           | true   |
|            10 | EQUALITY  | V1:"key2" | VARIANT           | true   |
+---------------+-----------+-----------+-------------------+--------+
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To drop search optimization for substrings on the column c2, execute the following statement:

ALTER TABLE t1 DROP SEARCH OPTIMIZATION ON SUBSTRING(c2);
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To drop search optimization for all methods on the column c5, execute the following statement:

ALTER TABLE t1 DROP SEARCH OPTIMIZATION ON c5;
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Because the column c5 is configured to optimize equality and substring searches, the statement above drops the configuration for equality and substring searches for c5.

To drop search optimization for equality on the column c1 and to drop the configuration specified by the expression IDs 6 and 8, execute the following statement:

ALTER TABLE t1 DROP SEARCH OPTIMIZATION ON EQUALITY(c1), 6, 8;
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For more information on the syntax, see the section on ALTER TABLE … DROP SEARCH OPTIMIZATION.

Removing Search Optimization From the Table

To remove the SEARCH OPTIMIZATION property from a table:

  1. Switch to a role that has the privileges to remove search optimization from the table.

  2. Run the ALTER TABLE … DROP SEARCH OPTIMIZATION command without the ON clause:

    ALTER TABLE [IF EXISTS] <table_name> DROP SEARCH OPTIMIZATION;
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    For example:

    alter table test_table drop search optimization;
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For more information, see the section on ALTER TABLE … DROP SEARCH OPTIMIZATION.

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