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Document special array constructor for PostgreSQL fixes #404

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Sean Corfield 2022-04-23 13:21:07 -07:00
parent 083833cd8b
commit 9e72587bf3
1 changed files with 43 additions and 19 deletions
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62
doc/postgresql.md
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@ -10,6 +10,49 @@ Everything that the nilenso library provided (in 0.4.112) is implemented
directly in HoneySQL 2.x although a few things have a
slightly different syntax.
## Code Examples
The code examples herein assume:
```clojure
(refer-clojure :exclude '[update set])
(require '[honey.sql :as sql]
'[honey.sql.helpers :refer [select from where
update set
insert-into values
create-table with-columns create-view create-extension
add-column alter-table add-index
modify-column rename-column rename-table
drop-table drop-column drop-index drop-extension
upsert returning on-conflict on-constraint
do-update-set do-nothing]])
```
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.
## Working with Arrays
HoneySQL supports `:array` as special syntax to produce `ARRAY[..]` expressions
but PostgreSQL also has an "array constructor" for creating arrays from subquery results.
```sql
SELECT ARRAY(SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%');
```
In order to produce that SQL, you can use HoneySQL's "as-is" function syntax to circumvent
the special syntax:
```clojure
user=> (sql/format {:select [[[:'ARRAY {:select :oid :from :pg_proc :where [:like :proname [:inline "bytea%"]]}]]]})
["SELECT ARRAY (SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%')"]
```
Compare this with the `ARRAY[..]` syntax:
```clojure
user=> (sql/format {:select [[[:array [1 2 3]] :a]]})
["SELECT ARRAY[?, ?, ?] AS a" 1 2 3]
```
## Operators with @
A number of PostgreSQL operators contain `@` which is not legal in a Clojure keyword or symbol (as literal syntax). The recommendation is to `def` your own name for these
@ -32,25 +75,6 @@ HoneySQL not to do that. There are two possible approaches:
1. Use named parameters (e.g., `[:param :myval]`) instead of having the values directly in the DSL structure and then pass `{:params {:myval some-json}}` as part of the options in the call to `format`, or
2. Use `[:lift ..]` wrapped around any structured values which tells HoneySQL not to interpret the vector or hash map value as a DSL: `[:lift some-json]`.
## Code Examples
The code examples herein assume:
```clojure
(refer-clojure :exclude '[update set])
(require '[honey.sql :as sql]
'[honey.sql.helpers :refer [select from where
update set
insert-into values
create-table with-columns create-view create-extension
add-column alter-table add-index
modify-column rename-column rename-table
drop-table drop-column drop-index drop-extension
upsert returning on-conflict on-constraint
do-update-set do-nothing]])
```
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.
## Upsert
Upserting data is relatively easy in PostgreSQL