diff options
Diffstat (limited to 'doc/development/iterating_tables_in_batches.md')
-rw-r--r-- | doc/development/iterating_tables_in_batches.md | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/doc/development/iterating_tables_in_batches.md b/doc/development/iterating_tables_in_batches.md index 9ea7fd3dc29..38cdbdf5b79 100644 --- a/doc/development/iterating_tables_in_batches.md +++ b/doc/development/iterating_tables_in_batches.md @@ -142,7 +142,7 @@ database query: SELECT "users"."id" FROM "users" ORDER BY "users"."id" ASC LIMIT 1 ``` -![Reading the start `id` value](img/each_batch_users_table_iteration_1_v13_7.png) +![Reading the start ID value](img/each_batch_users_table_iteration_1_v13_7.png) Notice that the query only reads data from the index (`INDEX ONLY SCAN`), the table is not accessed. Database indexes are sorted so taking out the first item is a very cheap operation. @@ -155,7 +155,7 @@ to get a "shifted" `id` value. SELECT "users"."id" FROM "users" WHERE "users"."id" >= 1 ORDER BY "users"."id" ASC LIMIT 1 OFFSET 5 ``` -![Reading the end `id` value](img/each_batch_users_table_iteration_2_v13_7.png) +![Reading the end ID value](img/each_batch_users_table_iteration_2_v13_7.png) Again, the query only looks into the index. The `OFFSET 5` takes out the sixth `id` value: this query reads a maximum of six items from the index regardless of the table size or the iteration @@ -181,7 +181,7 @@ previous iteration in order to find out the next end `id` value. SELECT "users"."id" FROM "users" WHERE "users"."id" >= 302 ORDER BY "users"."id" ASC LIMIT 1 OFFSET 5 ``` -![Reading the second end `id` value](img/each_batch_users_table_iteration_4_v13_7.png) +![Reading the second end ID value](img/each_batch_users_table_iteration_4_v13_7.png) Now we can easily construct the `users` query for the second iteration. |