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fixes #556 by documenting all the xtdb stuff
Signed-off-by: Sean Corfield <[email protected]>
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| Original file line number | Diff line number | Diff line change |
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| # XTDB Support | ||
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| As of 2.6.1230, HoneySQL provides support for most of XTDB's SQL | ||
| extensions, with additional support being added in subsequent releases. | ||
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| For the most part, XTDB's SQL is based on | ||
| [SQL:2011](https://en.wikipedia.org/wiki/SQL:2011), including the | ||
| bitemporal features, but also includes a number of SQL extensions | ||
| to support additional XTDB-specific features. | ||
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| HoneySQL attempts to support all of these XTDB features in the core | ||
| ANSI dialect, and this section documents most of those XTDB features. | ||
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| For more details, see the XTDB documentation: | ||
| * [SQL Overview](https://docs.xtdb.com/quickstart/sql-overview.html) | ||
| * [SQL Queries](https://docs.xtdb.com/reference/main/sql/queries.html) | ||
| * [SQL Transactions/DML](https://docs.xtdb.com/reference/main/sql/txs.html) | ||
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| ## Code Examples | ||
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| The code examples herein assume: | ||
| ```clojure | ||
| (refer-clojure :exclude '[update set]) | ||
| (require '[honey.sql :as sql] | ||
| '[honey.sql.helpers :refer [select from where | ||
| delete-from erase-from | ||
| insert-into patch-into values | ||
| records]]) | ||
| ``` | ||
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| Clojure users can opt for the shorter `(require '[honey.sql :as sql] '[honey.sql.helpers :refer :all])` but this syntax is not available to ClojureScript users. | ||
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| ## `select` Variations | ||
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| XTDB allows you to omit `SELECT` in a query. `SELECT *` is assumed if | ||
| it is omitted. In HoneySQL, you can simply omit the `:select` clause | ||
| from the DSL to achieve this. | ||
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| ```clojure | ||
| user=> (sql/format '{select * from foo where (= status "active")}) | ||
| ["SELECT * FROM foo WHERE status = ?" "active"] | ||
| user=> (sql/format '{from foo where (= status "active")}) | ||
| ["FROM foo WHERE status = ?" "active"] | ||
| ``` | ||
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| You can also `SELECT *` and then exclude columns and/or rename columns. | ||
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| ```clojure | ||
| user=> (sql/format '{select ((* {exclude _id rename ((title, name))}))}) | ||
| ["SELECT * EXCLUDE _id RENAME title AS name"] | ||
| user=> (sql/format '{select ((a.* {exclude _id}) | ||
| (b.* {rename ((title, name))})) | ||
| from ((foo a)) | ||
| join ((bar b) (= a._id b.foo_id))}) | ||
| ["SELECT a.* EXCLUDE _id, b.* RENAME title AS name FROM foo AS a INNER JOIN bar AS b ON a._id = b.foo_id"] | ||
| ``` | ||
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| ## Nested Sub-Queries | ||
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| XTDB can produce structured results from `SELECT` queries containing | ||
| sub-queries, using `NEST_ONE` and `NEST_MANY`. In HoneySQL, these are | ||
| supported as regular function syntax in `:select` clauses. | ||
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| ```clojure | ||
| user=> (sql/format '{select (a.* | ||
| ((nest_many {select * from bar where (= foo_id a._id)}) | ||
| b)) | ||
| from ((foo a))}) | ||
| ["SELECT a.*, NEST_MANY (SELECT * FROM bar WHERE foo_id = a._id) AS b FROM foo AS a"] | ||
| ``` | ||
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| Remember that function calls in `:select` clauses need to be nested three | ||
| levels of parentheses (brackets): | ||
| `:select [:col-a [:col-b :alias-b] [[:fn-call :col-c] :alias-c]]`. | ||
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| ## `records` Clause | ||
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| XTDB provides a `RECORDS` clause to specify a list of structured documents, | ||
| similar to `VALUES` but specifically for documents rather than a collection | ||
| of column values. HoneySQL supports a `:records` clauses and automatically | ||
| lifts hash map values to parameters (rather than treating them as DSL fragments). | ||
| You can inline a hash map to produce XTDB's inline document syntax. | ||
| See also `insert` and `patch` below. | ||
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| ```clojure | ||
| user=> (sql/format {:records [{:_id 1 :status "active"}]}) | ||
| ["RECORDS ?" {:_id 1, :status "active"}] | ||
| user=> (sql/format {:records [[:inline {:_id 1 :status "active"}]]}) | ||
| ["RECORDS {_id: 1, status: 'active'}"] | ||
| ``` | ||
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| ## `object` (`record`) Literals | ||
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| While `RECORDS` exists in parallel to the `VALUES` clause, XTDB also provides | ||
| a syntax to construct documents in other contexts in SQL, via the `OBJECT` | ||
| literal syntax. `RECORD` is a synonym for `OBJECT`. HoneySQL supports both | ||
| `:object` and `:record` as special syntax: | ||
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| ```clojure | ||
| user=> (sql/format {:select [[[:object {:_id 1 :status "active"}]]]}) | ||
| ["SELECT OBJECT (_id: 1, status: 'active')"] | ||
| user=> (sql/format {:select [[[:record {:_id 1 :status "active"}]]]}) | ||
| ["SELECT RECORD (_id: 1, status: 'active')"] | ||
| ``` | ||
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| ## Object Navigation Expressions | ||
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| In order to deal with nested documents, XTDB provides syntax to navigate | ||
| into them, via field names and/or array indices. HoneySQL supports this | ||
| via the `:get-in` special syntax, intended to be familiar to Clojure users. | ||
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| The first argument to `:get-in` is treated as an expression that produces | ||
| the document, and subsequent arguments are treated as field names or array | ||
| indices to navigate into that document. | ||
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| ```clojure | ||
| user=> (sql/format {:select [[[:get-in :doc :field1 :field2]]]}) | ||
| ["SELECT (doc).field1.field2"] | ||
| user=> (sql/format {:select [[[:get-in :table.col 0 :field]]]}) | ||
| ["SELECT (table.col)[0].field"] | ||
| ``` | ||
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| If you want an array index to be a parameter, use `:lift`: | ||
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| ```clojure | ||
| user=> (sql/format {:select [[[:get-in :doc [:lift 0] :field]]]}) | ||
| ["SELECT (doc)[?].field" 0] | ||
| ``` | ||
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| ## Temporal Queries | ||
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| XTDB allows any query to be run in a temporal context via the `SETTING` | ||
| clause (ahead of the `SELECT` clause). HoneySQL supports this via the | ||
| `:setting` clause. It accepts a sequence of identifiers and expressions. | ||
| An identifier ending in `-time` is assumed to be a temporal identifier | ||
| (e.g., `:system-time` mapping to `SYSTEM_TIME`). Other identifiers are assumed to | ||
| be regular SQL (so `-` is mapped to a space, e.g., `:as-of` mapping to `AS OF`). | ||
| A timestamp literal, such as `DATE '2024-11-24'` can be specified in HoneySQL | ||
| using `[:inline [:DATE "2024-11-24"]]` (note the literal case of `:DATE` | ||
| to produce `DATE`). | ||
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| See [XTDB's Top-level queries documentation](https://docs.xtdb.com/reference/main/sql/queries.html#_top_level_queries) for more details. | ||
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| Here's one fairly complex example: | ||
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| ```clojure | ||
| user=> (sql/format {:setting [[:basis-to [:inline :DATE "2024-11-24"]] | ||
| [:default :valid-time :to :between [:inline :DATE "2022"] :and [:inline :DATE "2023"]]]}) | ||
| ["SETTING BASIS TO DATE '2024-11-24', DEFAULT VALID_TIME TO BETWEEN DATE '2022' AND DATE '2023'"] | ||
| ``` | ||
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| Table references (e.g., in a `FROM` clause) can also have temporal qualifiers. | ||
| See [HoneySQL's `from` clause documentation](clause-reference.md#from) for | ||
| examples of that, one of which is reproduced here: | ||
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| ```clojure | ||
| user=> (sql/format {:select [:username] | ||
| :from [[:user :for :system-time :as-of [:inline "2019-08-01 15:23:00"]]] | ||
| :where [:= :id 9]}) | ||
| ["SELECT username FROM user FOR SYSTEM_TIME AS OF '2019-08-01 15:23:00' WHERE id = ?" 9] | ||
| ``` | ||
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| ## `delete` and `erase` | ||
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| In XTDB, `DELETE` is a temporal deletion -- the data remains in the database | ||
| but is no longer visible in queries that don't specify a time range prior to | ||
| the deletion. XTDB provides a similar `ERASE` operation that can permanently | ||
| delete the data. HoneySQL supports `:erase-from` with the same syntax as | ||
| `:delete-from`. | ||
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| ```clojure | ||
| user=> (sql/format {:delete-from :foo :where [:= :status "inactive"]}) | ||
| ["DELETE FROM foo WHERE status = ?" "inactive"] | ||
| user=> (sql/format {:erase-from :foo :where [:= :status "inactive"]}) | ||
| ["ERASE FROM foo WHERE status = ?" "inactive"] | ||
| ``` | ||
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| ## `insert` and `patch` | ||
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| XTDB supports `PATCH` as an upsert operation: it will update existing | ||
| documents (via merging the new data) or insert new documents if they | ||
| don't already exist. HoneySQL supports `:patch-into` with the same syntax | ||
| as `:insert-into` with `:records`. | ||
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| ```clojure | ||
| user=> (sql/format {:insert-into :foo | ||
| :records [{:_id 1 :status "active"}]}) | ||
| ["INSERT INTO foo RECORDS ?" {:_id 1, :status "active"}] | ||
| user=> (sql/format {:patch-into :foo | ||
| :records [{:_id 1 :status "active"}]}) | ||
| ["PATCH INTO foo RECORDS ?" {:_id 1, :status "active"}] | ||
| ``` |
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