Add some docs for postgres fts

website/site/content/docs/configure/_index.md

@@ -177,17 +177,37 @@ this account and setup the notification hooks in there - not in your
 normal account.
 
 
-## Full-Text Search: SOLR
+## Full-Text Search
 
-[Apache SOLR](https://solr.apache.org) is used to provide the
-full-text search. Both docspell components must provide the same
-connection setup. This is defined in the `full-text-search.solr`
+Fulltext search is optional and provided by external systems. There
+are currently [Apache SOLR](https://solr.apache.org) and [PostgreSQL's
+text search](https://www.postgresql.org/docs/14/textsearch.html)
+available.
+
+You can enable and configure the fulltext search backends as described
+below and then choose the wanted backend:
+
+```conf
+full-text-search {
+  enabled = true
+  # Which backend to use, either solr or postgresql
+  backend = "solr"
+  …
+}
+```
+
+All docspell components must provide the same fulltext search
+configuration.
+
+### SOLR
+
+[Apache SOLR](https://solr.apache.org) can be used to provide the
+full-text search. This is defined in the `full-text-search.solr`
 subsection:
 
 ``` bash
 ...
   full-text-search {
-    enabled = true
     ...
     solr = {
       url = "http://localhost:8983/solr/docspell"
@@ -247,6 +267,79 @@ The solr index doesn't contain any new information, it can be
 regenerated any time using the above REST call. Thus it doesn't need
 to be backed up.
 
+### PostgreSQL
+
+PostgreSQL provides many additional features, one of them is [text
+search](https://www.postgresql.org/docs/14/textsearch.html). Docspell
+can utilize this to provide the fulltext search feature. This is
+especially useful, if PostgreSQL is used as the primary database for
+docspell.
+
+You can choose to use the same database or separate connection. The
+fulltext search will create a single table `ftspsql_search` that holds
+all necessary data. When doing backups, you can exclude this table as
+it can be recreated from the primary data any time.
+
+The configuration is placed inside `full-text-search`:
+
+```conf
+full-text-search {
+  …
+  postgresql = {
+    use-default-connection = false
+
+    jdbc {
+      url = "jdbc:postgresql://server:5432/db"
+      user = "pguser"
+      password = ""
+    }
+
+    pg-config = {
+    }
+    pg-query-parser = "websearch_to_tsquery"
+    pg-rank-normalization = [ 4 ]
+  }
+}
+```
+
+The flag `use-default-connection` can be set to `true` if you use
+PostgreSQL as the primary db to have it also used for the fulltext
+search. If set to `false`, the subsequent `jdbc` block defines the
+connection to the postgres database to use.
+
+It follows some settings to tune PostgreSQL's text search feature.
+Please visit [their
+documentation](https://www.postgresql.org/docs/14/textsearch.html) for
+all the details.
+
+- `pg-config`: this is an optional mapping from document languages as
+  used in Docspell to a PostgreSQL text search configuration. Not all
+  languages are equally well supported out of the box. You can create
+  your own text search config in PostgreSQL and then define it in this
+  map for your language. For example:
+
+  ```conf
+  pg-config = {
+    english = "my-english"
+    german = "my-german"
+  }
+  ```
+
+  By default, the predefined configs are used for some lanugages and
+  otherwise fallback to `simple`.
+
+  *If you change this setting, you must re-index everything.*
+- `pg-query-parser`: the parser applied to the fulltext query. By
+  default it is `websearch_to_tsquery`. (relevant [doc
+  link](https://www.postgresql.org/docs/14/textsearch-controls.html#TEXTSEARCH-PARSING-QUERIES))
+- `pg-rank-normalization`: this is used to tweak rank calculation that
+  affects the order of the elements returned from a query. It is an
+  array of numbers out of `1`, `2`, `4`, `8`, `16` or `32`. (relevant
+  [doc
+  link](https://www.postgresql.org/docs/14/textsearch-controls.html#TEXTSEARCH-RANKING))
+
+
+
 ## Bind
 
 The host and port the http server binds to. This applies to both

website/site/content/docs/install/download_run.md

@@ -110,7 +110,7 @@ Fulltext search is powered by [SOLR](https://solr.apache.org). You
 need to install solr and create a core for docspell. Then cange the
 solr url for both components (restserver and joex) accordingly. See
 the relevant section in the [config
-page](@/docs/configure/_index.md#full-text-search-solr).
+page](@/docs/configure/_index.md#full-text-search).
 
 
 ### Watching a directory