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Creating a Table Materialization

In the previous example, our model was materialized as a view. While this might offer sufficient performance for some queries, more complex SELECTs or frequently executed queries may be better materialized as a table. This materialization is useful for models that will be queried by BI tools to ensure users have a faster experience. This effectively causes the query results to be stored as a new table, with the associated storage overheads - effectively, an INSERT TO SELECT is executed. Note that this table will be reconstructed each time i.e., it is not incremental. Large result sets may therefore result in long execution times - see dbt Limitations.

  1. Modify the file actors_summary.sql such that the materialized parameter is set to table. Notice how ORDER BY is defined, and notice we use the MergeTree table engine:

    {{ config(order_by='(updated_at, id, name)', engine='MergeTree()', materialized='table') }}
  2. From the imdb directory execute the command dbt run. This execution may take a little longer to execute - around 10s on most machines.

    [email protected]:~/imdb$ dbt run
    15:13:27 Running with dbt=1.0.4
    15:13:27 Found 1 model, 0 tests, 1 snapshot, 0 analyses, 181 macros, 0 operations, 0 seed files, 6 sources, 0 exposures, 0 metrics
    15:13:28 Concurrency: 1 threads (target='dev')
    15:13:28 1 of 1 START table model imdb_dbt.actor_summary................................. [RUN]
    15:13:37 1 of 1 OK created table model imdb_dbt.actor_summary............................ [OK in 9.22s]
    15:13:37 Finished running 1 table model in 10.20s.
    15:13:37 Completed successfully
    15:13:37 Done. PASS=1 WARN=0 ERROR=0 SKIP=0 TOTAL=1
  3. Confirm the creation of the table imdb_dbt.actor_summary:

    SHOW CREATE TABLE imdb_dbt.actor_summary;

    You should the table with the appropriate data types:

    |CREATE TABLE imdb_dbt.actor_summary
    |`id` UInt32,
    |`first_name` String,
    |`last_name` String,
    |`num_movies` UInt64,
    |`updated_at` DateTime
    |ENGINE = MergeTree
    |ORDER BY (id, first_name, last_name)
    |SETTINGS index_granularity = 8192
  4. Confirm the results from this table are consistent with previous responses. Notice an appreciable improvement in the response time now that the model is a table:

    SELECT * FROM imdb_dbt.actor_summary ORDER BY num_movies DESC LIMIT 5;
    |id |name |num_movies|avg_rank |genres|directors|updated_at |
    |45332 |Mel Blanc |832 |6.175853582979779 |18 |84 |2022-04-26 15:26:55|
    |621468|Bess Flowers|659 |5.57727638854796 |19 |293 |2022-04-26 15:26:57|
    |372839|Lee Phelps |527 |5.032976449684617 |18 |261 |2022-04-26 15:26:56|
    |283127|Tom London |525 |2.8721716524875673|17 |203 |2022-04-26 15:26:56|
    |356804|Bud Osborne |515 |2.0389507108727773|15 |149 |2022-04-26 15:26:56|

    Feel free to issue other queries against this model. For example, which actors have the highest ranking movies with more than 5 appearances?

    SELECT * FROM imdb_dbt.actor_summary WHERE num_movies > 5 ORDER BY avg_rank  DESC LIMIT 10;