data can “get in” from all sort of ways (throwaway SQL scripts for example) Even if today your database is used only by a single app, you might have more than one in the future and adding indexes on existing Sep 14, 2023 · If this oid is just a normal column and using a sequence, you can use a conditional unique constraint: CREATE UNIQUE INDEX u_column ON your_table(your_unique_column) WHERE oid > _current_max_value; Just check the value for your oid where the unique constraint should start. nspname as index_schema, tbl. Jul 18, 2018 · But a UNIQUE index is absolute and still has to consider concurrently entered rows - even yet invisible rows. ON table_name (expression); Code language: SQL (Structured Query Language) (sql) In this statement: First, specify the index name Aug 19, 2012 · Partial unique indexes cannot be created with CONSTRAINT constraint_name UNIQUE(columns) in PostgreSQL. Otherwise it returns email. An index allows the database server to find and retrieve specific rows much faster than it could do without an index. CREATE UNIQUE INDEX reference_count_unique_index ON How to add a conditional unique index on PostgreSQL. So, col1 and col2 can repeat, but not at the same time. So you can get an exception for a unique violation, but you still cannot see the conflicting row within the same query. Step 3. I'm not trying anything crazy, just adding historic values. Feb 5, 2021 · We are considering using dbt to manage models in our PostgreSQL data warehouse. The name of an index-method-specific storage parameter. Unique constraints are enforced (behind the scenes) by unique indexes. An index column need not be just a column of the underlying table, but can be a function or scalar expression computed from one or more columns of the table. COPY proposals (proposal, user_id, draft) FROM stdin; Enter data to be copied followed by a newline. Also google Mar 20, 2015 · Not sure if this is possible in PostgreSQL 9. To create an UNIQUE index, you can use the following syntax: CREATE UNIQUE INDEX index_name ON table_name(column_name, []); The keyword UNIQUE is used to declare an index as unique. Mar 4, 2022 · I want to make sure that inserting the last one here would have failed, because it's the same as ID 1 but reversed. Examining Index Usage. For instance: id int PRIMARY KEY AUTOINCREMENT, col1 int NOT NULL, col2 int NOT NULL. indexrelid join pg_namespace insp on insp. I would like to set up a table in PostgreSQL such that two columns together must be unique. But this constraint must allow multiple "primary" = 'N' customers with same pe number. 11. But you'll still see a sequential scan. For a table like: CREATE TABLE data ( id SERIAL , day DATE , val NUMERIC ); CREATE INDEX data_day_val_idx ON data (day, val); I'd like to be able to [quickly] query only the distinct days. CREATE UNIQUE INDEX name ON table ( column [, ]) [ NULLS [ NOT ] DISTINCT ]; Currently, only B-tree indexes can be declared unique. Only the new values must be unique. 11. unique and Column. 20. The rest of the answer describes the buggy behavior: As you found out, you can only specify the expression for a unique constraint and not the one for a unique index. col3 + 1; ERROR: there is no unique or exclusion constraint matching the ON CONFLICT specification. sql_create_unique_index else: sql = self. Aug 27, 2018 · SET enable_seqscan = OFF; Then: EXPLAIN. PostgreSQL will build an index for rows that satisfy the predicate. May 10, 2021 · In other words, a "primary" customer row can only have one flagged 'Y' for each pe number. Below is the query and the query plan output. Indexes and Collations. The manual: I am attempting to apply an Unique Index in Postgresql with mixed results. CREATE UNIQUE INDEX name ON table ( column [, ]); Currently, only B-tree indexes can be declared unique. @a_horse_with_no_name: but the condition would apply to all rows of the table :) there can only be one unique(a,b) where b is true, which is compared to each record. The index for the first case is tiny, holding one or no row. A major motivation for partial indexes is to avoid indexing common values. They work by creating a separate data structure that contains a subset of the data in the table, organized in a way that makes it easy to search. Two reasons for that: let the DBMS do its job, it was built to check constraints. Also, updates on a row that is not included in a conditional index do not have to spend time updating the index. after that, I added the _deleted for soft deletes. . Create two partial indexes: Jun 24, 2019 · You need to use pg_index and limit to those that have indisunique. Modify the @@unique modifier to include a where: { } argument that could define the condition that allows this to be unique. 1) Unique indexes for a primary key column and a column with a unique constraint. A partial index is an index built on a subset of data of the indexed columns. relname as index_name, insp. MSSQL) allow only a single null in such cases. PostgreSQL UNIQUE index examples. Functional indexes can be used to obtain fast access to data based on the result of function calls. Jun 18, 2024 · Constraints can be named explicitly using the Constraint. Id, b. An access method that supports this feature sets amcanunique true. The unique index provides speedy searches since it allows operations such as Index Range Scan and Index Seeks. Partial Indexes. We will now consider B-tree, the most traditional and widely used index. insert into posts(id, title, body) values (1, 'First post', 'Awesome') on conflict (title, body) do nothing; Jul 18, 2020 · Problem tl;dr - Support for Postgres Partial Indexes and related functionality Consider, for ex, a versioned CMS schema model Page { id Int @id @default(autoincrement) staticId String isLatest Bool The NULLS NOT DISTINCT option modifies this and causes the index to treat nulls as equal. DO UPDATE SET col3 = 'c', col2 = 2. However, remember that maintaining this index has a performance cost during data insertion and updates. You can use CASE expressions in SELECT statements as well as WHERE, GROUP BY, and HAVING clauses. Remove uniqueness of index in PostgreSQL. I am generating the index via a Ruby on Rails migration. Fortunately, this can be done. (At present, only b-tree supports it. In addition to simply finding the rows to be returned by a query, an index may be able to deliver them in a specific sorted order. CREATE INDEX ON mytable (id) WHERE time BETWEEN '2018-10-01 00:00:00' AND '2018-10-03 23:59:59'; The BRIN index is probably useless because the physical order of the tuples in the May 19, 2015 · Instead of using the text data type, we can use the citext (case insensitive text) type! First we need to enable the citext extension: Then we'll need to change the email data type in the users table: Now our existing UNIQUE constraint should be case insensitive! DETAIL: Key ( email)=(TEST@example. We could write (CASE WHEN booking_status = 1 THEN TRUE END) as (booking_status = 1 OR NULL) if that makes it any more clear. name TEXT NOT NULL, value TEXT NOT NULL, PRIMARY KEY (name, value) ); I frequently do a query to see what value s are available: SELECT DISTINCT value FROM items; May 28, 2012 · 3. tablespace_name. He can have as many disabled toggles he needed Mar 1, 2016 · SELECT * FROM line WHERE date = CURRENT_DATE; As an aside, if you're on Postgres 9. This syntax seems to be designed for a single composite unique constraint over two columns, rather than two constraints. You will still use an index however I think each check would cost you more points. The index contains entries only for those table rows that satisfy the predicate. I do object to the last statement, current_date will use index in that particular query. name parameter. When you perform a query that includes a search condition, PostgreSQL can use the index Jan 24, 2023 · While the SQL standard allows multiple nulls in a unique column, and that is how Postgres behaves, some database systems (e. I have a PostgreSQL table that looks like this: CREATE TABLE items (. It does so by searching if there are rows in the source table that would become orphaned by the data modification. HasIndex(b => new { b. To define a subset of data, you use a predicate, which is a conditional expression, of the partial index. PostgreSQL enforces SQL uniqueness constraints using unique indexes, which are indexes that disallow multiple entries with identical keys. Here’s the basic syntax for creating an index on expression: CREATE INDEX index_name. ON table_name(column_name, []); Note: O nly B-tree indexes can be declared as unique indexes. Indexes and ORDER BY #. Example: import { Entity, PrimaryGeneratedColumn, Column, Index } from "typeorm" @Entity() export class User { @PrimaryGeneratedColumn() id: number @Index() @Column() firstName Aug 15, 2016 · Important note: This behavior can only be observed on versions before 9. Put the equality-match columns first in the index, then the range match (COL_TIME >= ?) column. If the column type is boolean (likely should be), you can simplify: CREATE UNIQUE INDEX tbl_some_name_idx ON tbl (subset) WHERE type; This way you can even make combinations with NULL unique, which wasn't Indexes. There are also the use cases of using the Column. You delete rows or update key columns in the target table. You can create the index and transform the field to upper- or lower-case. Probably the best option if you absolutely must guarantee uniqueness would be to have a separate table of deleted posts. index parameters which create UniqueConstraint and Index objects without an explicit name being Mar 9, 2016 · First you have to create a table unique constraint on the columns col1, col2 Then once you do that you can do the following: INSERT INTO dupes values(3,2,'c') ON CONFLICT ON CONSTRAINT dupes_pkey. Indexes. Using PostgreSQL 9. Of the index types currently supported by PostgreSQL, only B-tree can produce sorted output Consider also using a filtered index, which is equivalent in terms of functionality but would be using less space, as it will be storing the j values only for rows with i = 1 and not the (possibly millions) or the rest NULL values: CREATE UNIQUE INDEX test_index_2 ON test (j) WHERE i=1 ; You can create a database index for a specific column by using @Index on a column you want to make an index. db import models class Model(models. Let’s explore some examples of using the PostgreSQL unique indexes. new_name. If you expect to perform a lot of searches based on a column, a UNIQUE constraint can be beneficial beyond enforcing data integrity. Jun 14, 2017 · The condition is that the Name is unique only when "Expired" is false. Indexes can also be used to enforce uniqueness of a column's value, or the uniqueness of the combined values of more than one column. 6. You have the unique index on the main table, but not on the table containing deleted records. My table layout: Apr 19, 2007 · NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "proposals_pkey" for table "proposals" CREATE TABLE-- Here's the partial unique index: CREATE UNIQUE INDEX one_draft_proposal_per_user ON proposals (user_id) WHERE draft; CREATE INDEX. Unique and exclude constraints accept rows where one or more of the expressions is NULL. CREATE UNIQUE INDEX reference_count_unique_index ON Oct 1, 2018 · If the time interval is variable, your original index is perfect (that's why PostgreSQL is using it). If the time interval is constant, the perfect index would be. You want to create an index that contains the records you do want. Model): class Meta: unique_together = ['a', 'b'] a = models. create unique index unique_test_index on unique_test(number, boolean) where active; insert into unique_test values (1, true); -- ERROR: duplicate key value violates unique constraint "unique_test_index" A PostgreSQL CASE expression is a conditional expression that works the same as an if-else statement in other programming languages. But indexes also add overhead to the database system as a whole, so they should be used sensibly. You can create indices for any columns of your entity. Since dbt models are SQL select statements, there doesn't seem to be an obvious, or documented, way to specify that a particular column should have an index. g. This is only useful if you want to experiment with partial indexes directly in PostgreSQL, if you've already SQLAlchemy set up, take the approach below and just initialize your database. This is a bug that was fixed in 9. However, since the update only applies to an unindexed column, it is fast. Share Sep 1, 2021 · if condition or include or opclasses: sql = self. answered Mar 1, 2016 at 14:10. Typically cleanest and fastest: SELECT category , count(*) FILTER (WHERE question1 = 0) AS zero , count(*) FILTER (WHERE question1 = 1) AS one , count(*) FILTER (WHERE question1 = 2) AS two FROM reviews GROUP BY 1; Details for the FILTER clause: Dec 28, 2015 · How to add a conditional unique index on PostgreSQL; Why use an index and not a constraint? Addressing your question in the comment: This is an index, not a CONSTRAINT. We used a non-indexed tombstone boolean column called deleted with a DEFAULT FALSE. The index covers the columns that make Description. 4 or later, use the aggregate FILTER option. constraints. Note that the indexes on expressions are also known as functional indexes. Indexes are primarily used to enhance database performance (though inappropriate use can result in slower performance). This partial index can enhance query performance while reducing the index size. One should always use the semantically better suitable way, and in this case I agree with you that this would be a constraint, not an index. extension_name. ForeignKey('some_model', null=True) b = models. However, in the case of constraints this parameter is optional. 12. MySQL. In a partial index, the list is just smaller: there are only index entries for rows that meet the condition. There can be multiple values of either value, so long as there are not two that share both. 1. Nick Barnes. Creating such a table can be done in the following steps. Use the following code to specify an operator class: . 8k 4 57 67. Apr 27, 2016 · INSERT INTO mytable(col1, col2, col3) VALUES ('A', 'B', 0) ON CONFLICT (col1, col2) DO UPDATE SET col3 = EXCLUDED. com) already exists. table_constraints; Then if you find one, you should be able to drop it like: ALTER TABLE <my_table> DROP CONSTRAINT <constraint_name>. PostgreSQL uses unique indexes to implement unique constraints, so the effect is the same, with an important caveat: you can't perform upserts ( ON CONFLICT DO UPDATE ) against a unique index like you would against a unique I would like to be able to define a uniqueness constraint that has conditional elements to it so that it can map to and align with a conditional unique index/constraint within the database. Users migrating from other database systems sometimes want to emulate this behavior in Postgres. The up statement looks like: execute ("create unique index formatted_address_unit_number_and_status on properties (formatted_address, unit_number) where status = 'published';") remove_foreign_key :editabilities, column: :user_id remove_index :editabilities, :user_id add_index :editabilities, :user_id, unique: true end If you rely on the index in your production database you might want to add a new modified index first with a different name, so you have two indices. 627k 151 1. Jun 25, 2003 · isbs=# create unique index person_login on person (login) where login<>''; Postgres start to use conditional index only when I also pass index' condition: Functional Indexes. If a column is defined as a unique index, then the column cannot store duplicated values. CREATE UNIQUE INDEX fk_client ON user_client (fk_client) WHERE fk_client NOT IN(SELECT fk_client FROM legal_entity); But It is not possible, because there is allowed run a sub query in the creation of an index. You may be able to remove the unique CONSTRAINT, and not the INDEX itself. Nov 1, 2010 · There is a nice way of doing conditional INSERT in PostgreSQL using WITH query: Like: WITH a as( select id from schema. name and surname cannot be duplicated, so I had a unique constraint on them and everything was good. – LongBeard_Boldy. 114. Sep 6, 2020 · A b-tree index can be thought of an ordered list of index entries, each with a pointer to a row in the table. DEMO If this is the case you need a unique constraint. Plus, that information can be picked up by information_schema to do some metadata inferring if necessary on the fact that both need to be unique. Unique Indexes. When you define a primary key or a unique constraint for a table, PostgreSQL automatically creates a corresponding unique index. The INDEX would look like this: CREATE UNIQUE INDEX [IX_Person] ON Person(Name) WHERE [Expired] = 0; Is there some way to write this unique index with code-first and not having to execute this SQL in a migration? I can write this: Note. 7. FROM mytable m. e. This feature is useful to obtain fast access to tables based on the results of computations. See: Specifying an Index (Non-Unique Key) Using JPA; JPA: defining an index column; Some JPA providers offer extension annotations By using a Partial Indexes this becomes simpler by placing a unique index on only non-deleted users: Conditional Constraints There are times where you may want data constraints, but only want them to exist in certain cases. Create two partial indexes: With Postgres 10 properly supporting hash index, I would like to use hash index for id lookup (hash index is smaller in size compared to btree and theoretically faster). When an index is declared unique, multiple table rows with equal indexed In Postgres 9. nspname as table_schema from pg_index pgi join pg_class idx on idx. When an index is declared unique, multiple table rows with equal indexed We've already discussed PostgreSQL indexing engine and interface of access methods , as well as hash index , one of access methods. In general however, your answer is absolutely correct. Example of good table: Dec 4, 2020 · While Postgres doesn't allow a partially unique constraint, it does support a partial unique index: create unique index unique_row on myTable(content_id, brand_id) where not is_archived; See Partial Indexes in the Postgres documentation. 1k 1. The index for the second case holds one row per existing userid, but it's the cheapest and fastest way, in addition Mar 2, 2021 · On PostgreSQL, I have a table with the columns name, surname and _deleted. Then you can remove the old index and afterwards Mar 3, 2017 · DEFERRABLE INITIALLY DEFERRED ; The CASE expression becomes NULL when booking_status is null or different than 1. The same clause works for a UNIQUE index, too: CREATE UNIQUE INDEX favo_uni_idx ON favorites (user_id, menu_id, recipe_id) NULLS NOT DISTINCT; Note the position of the new clause after the key fields. Sorted by: 2. – Jan 3, 2020 · This unique index will only contain rows satisfying the specified WHERE condition. This way, a unique index will be created behind the scenes, and you will get the behavior you need. Then when you do your queries, you can do the same transform and it'll do the right thing. Postgres 14 or older. Erwin Brandstetter. Take an example case where you don’t want to physically delete users, but rather wish to logically delete them. 3+, but I'd like to create a unique index on a non-unique column. PostgreSQL indexes are data structures that allow you to quickly search for specific data in a database table. I use PGSQL and try add the index below. Indexes are a common way to enhance database performance. This article is large, so be patient. Therefore, make sure the index expression returns NULL for every row where list_type <> 'default'. PostgreSQL does not support CHECK constraints that reference table data other than the new or updated row being checked. Either alter column datatype or CAST the value to CHAR in the index expression. The name (possibly schema-qualified) of an existing index to alter. For example, a common way to do case-insensitive comparisons is to use Only indexes of index type B-Tree can be declared as unique indexes. Without an index, this requires a sequential scan of the source table. It's only an implementation detail that PostgreSQL creates a unique index for a unique constraint at all. One user must have only one type of toggle enabled. CREATE INDEX constructs an index on the specified column (s) of the specified relation, which can be a table or a materialized view. 5. Design your indexes to match Oct 20, 2010 · 103. Here is the syntax of the PostgreSQL CASE expression: Explanation: Apr 23, 2017 · Step 2. This allows a query's ORDER BY specification to be honored without a separate sorting step. storage_parameter. exclusion-constraint. table_name (col_name1, col_name2) SELECT (col_name1, col_name2) WHERE NOT EXISTS ( SELECT id FROM a ) RETURNING id Sep 1, 2022 · if you create a unique key constraint on title & body columns, you can use insert statement as below to ignore if record already exists. Given, type can have values A-F, there can only be one A per date, but there can be multiple B-F. In PostgreSQL, the UNIQUE index to ensure the uniqueness of values in one or more columns. PostgreSQL automatically creates a unique index when a unique constraint or primary key is defined for a table. If you have a lot of transactions from different clients at the same time, it's possible for two of them to try and insert rows that individually are fine but shouldn't be allowed together (e. 4. Looking at PostgreSQL documentation, you could just use the statement below to create a new unique index. PostgreSQL allows you to specify operator classes on your indexes, to allow tweaking how the index should work. Corner case exception: If an index-only scan is possible, the index might still be used if it's substantially smaller than the table. 2. Again, postgresql can random-access the index to the first eligible row, then scan the index sequentially until it gets to the last eligible row. oid = pgi. You can do what you are already thinking of: create a unique constraint on both fields. Check your CONSTRAINTS via select * from information_schema. postgresql. In my case I was somewhat new to the concept of partial indexes and wanted PostgreSQL doesn't define a partial (i. A partial index is an index built over a subset of a table; the subset is defined by a conditional expression (called the predicate of the partial index). ForeignKey('some_other_model') # Works like a charm! b = B() Model This type of index is called an index on expression. A multicolumn unique index will only reject cases where all indexed columns are equal in multiple rows. CREATE INDEX findDaNulls ON othertable ((COALESCE(col1,col2,col3,'Empty'))) WHERE col1 IS NULL AND col2 IS NULL AND col3 IS NULL; SELECT *. Conceptually: The unique constraint defines the uniqueness. Create a unique index on a non Sep 10, 2016 · Unique indexes are useful to avoid duplicated records, but we needed a conditional unique index. And it's important to not have any rules on FROM_ID to be higher or lower than TO_ID as it should be possible to merge any 2 records and either have some automation or a user via frontend to choose who is the winner record. The name of the extension that the index is to depend on. It is not possible to have a conditional database index with most databases e. For example, a common way to do case-insensitive comparisons is to use the lower function: This query Nov 4, 2016 · Create an example table. name parameter, and for indexes the Index. If you have the index condition in your WHERE clause, PostgreSQL knows it can use the index and doesn't have to check the index Sep 23, 2023 · The UNIQUE constraint also creates a unique B-tree index on the column, which can speed up data retrieval. Before: from django. For a functional index, an index is defined on the result of a function applied to one or more columns of a single table. You would end up with a smaller posts Jan 1, 2012 · The index-only scans are a life saver and it wouldn't be possible without. I have a table create table t (id int); create unique index on t using hash (id); But I got the following: ERROR: access method "hash" does not support unique indexes . Our query now became: This definitely runs quicker (60-200%), but seems to ignore the col_name index for large IN clauses. 3k. Mar 9, 2016 · First you have to create a table unique constraint on the columns col1, col2 Then once you do that you can do the following: INSERT INTO dupes values(3,2,'c') ON CONFLICT ON CONSTRAINT dupes_pkey. one inserts (1, 2, 23) the other (1, 2, 22)), but since they don't see each other's work and at the time of transaction neither has committed, they'll be both allowed to insert/update the rows. You need to enclose the CASE expression in parentheses: CREATE INDEX IX_INDEXNAME ON SOME_TABLE ( (CASE WHEN COLUMN1 = 0 AND COLUMN2 = 'value' THEN SOME1_ID ELSE SOME2_ID END) ); answered Jan 19, 2015 at 19:34. Unique Indexes #. Partial indexes aren't going to help you here as they'll only find the records you don't want. Unique constraints already compare the current tuple May 22, 2023 · Attempt 1 - Creating a unique index. HasOperators(null, "text_pattern_ops"); Note that each operator class is used for the corresponding index column, by order. Mar 3, 2017 · DEFERRABLE INITIALLY DEFERRED ; The CASE expression becomes NULL when booking_status is null or different than 1. SELECT * FROM tbl ORDER BY ORDER BY x, y DESC; Now, if the index could be used in any way, it would be. table_name where column_name = your_identical_column_value ) INSERT into schema. May 22, 2023 · Attempt 1 - Creating a unique index. Name }) . Sep 28, 2021 · you would want an index on (COL_1, COL_3, COL_TIME). Dec 12, 2022 · I already use a trigger to check the uniqueness, but it creates problems for multi-threaded row recording because when two transactions write two identical rows simultaneously, the trigger performs a uniqueness check for transactions and since the trigger works BEFORE applying the transaction, there are no conflicting records in the database at the time of checking, the check is successful and Conditional Unique Index. The index contains entries for only those table rows that satisfy the predicate. 64. Suggested solution. The unique index implements the unique constraint. 5, this table might be a good candidate for a BRIN index. The key field (s) for the index are specified as column names, or alternatively Jun 12, 2011 · 1. Aug 2, 2012 · 4. conditional) UNIQUE constraint - however, you can create a partial unique index. When an index is declared unique, multiple table Apr 21, 2021 · Sure thing. Postgres using an index either way is an implementation detail. How can we specify column indexes on dbt models? type AS TEXT NOT NULL, CONSTRAINT unique_dt_type UNIQUE(dt,type) -- check constraint(?) ) Having a brain-dud when trying to think of the right syntax to create a unique constraint when only a certain condition exists. Postgres Pro automatically creates a unique index when a unique constraint or primary key is defined for a table. While a CHECK constraint that violates this rule may appear to work in simple tests, it cannot guarantee that the database will not reach a state in which the constraint condition is false (due to subsequent changes of the other row(s) involved). The ConditionalUniqueIndex lets you create partial unique indexes in case you ever need unique together constraints on nullable columns. sql_create_unique But I don't have such condition or opclasses in this case update Conditional Unique Index \n The ConditionalUniqueIndex lets you create partial unique indexes in case you ever need unique together constraints\non nullable columns. Jan 19, 2015 · 1 Answer. oid = idx The same clause works for a UNIQUE index, too: CREATE UNIQUE INDEX favo_uni_idx ON favorites (user_id, menu_id, recipe_id) NULLS NOT DISTINCT; Note the position of the new clause after the key fields. If a Oct 9, 2023 · The doc. But MySQL does not allow to index TEXT column. relname as table_name, tnsp. Further reading. I get the following error: May 28, 2020 · correspond to actual unique indexes in PostgreSQL. Unique index in one table. Index Uniqueness Checks #. The index covers the columns that make up the primary key or unique constraint (a multicolumn index, if appropriate), and is the mechanism that enforces the constraint. 2, I have troubles with slow queries on a relatively large table (200+ million rows). So: CREATE UNIQUE INDEX lower_case_username ON users ((lower(username))); Then query for the same thing: 8. Jun 7, 2012 · Querying table would result in index scan. Mar 23, 2015 · 6. First, create a table called Oct 9, 2020 · A partial unique index will do that: CREATE UNIQUE INDEX tbl_some_name_idx ON tbl (subset) WHERE type = 'true'; Data type does matter. The tablespace to which the index will be moved. Example 1: Jun 12, 2009 · Explanation: A unique index should not care about NULL values. Then PostgreSQL has to check if the foreign key constraint is still satisfied. unique-constraint. The new name for the index. To create a UNIQUE index, you can use the following syntax: Syntax: CREATE UNIQUE INDEX index_name. Btree Structure B-tree index type, implemented as "btree" access method, is suitable for data that can be sorted. ) Columns listed in the INCLUDE clause are not considered when 11. In other words, "greater", "greater or Mar 11, 2022 · CREATE UNIQUE INDEX auth0_users_email_idx ON users ((CASE WHEN id NOT LIKE 'auth0|%' THEN email END)); If the prefix matches then CASE returns NULL which is not checked for uniqueness. user330315 user330315. Indexes on Expressions. Aug 28, 2020 · Last Updated : 28 Aug, 2020. To get the actual index and table names, you need to join that table to pg_class and pg_namespace: select idx. 4. Depending on the percentage of matching rows, this may save a bit of storage space, or a lot relative to a full index. edited May 10, 2021 at 1:59. qr lq cd im it wd jt bs te lv