29 lines
1.3 KiB
SQL
29 lines
1.3 KiB
SQL
/* Copyright 2022 The Matrix.org Foundation C.I.C
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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-- next_token_id is a foreign key reference, so previously required a table scan
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-- when a row in the referenced table was deleted.
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-- As it was self-referential and cascaded deletes, this led to O(t*n) time to
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-- delete a row, where t: number of rows in the table and n: number of rows in
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-- the ancestral 'chain' of access tokens.
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--
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-- This index is partial since we only require it for rows which reference
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-- another.
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-- Performance was tested to be the same regardless of whether the index was
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-- full or partial, but a partial index can be smaller.
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CREATE INDEX refresh_tokens_next_token_id
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ON refresh_tokens(next_token_id)
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WHERE next_token_id IS NOT NULL;
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