From 7d5bc64196ea68dc89bb0f3777e681662865cfba Mon Sep 17 00:00:00 2001 From: "David E. Wheeler" Date: Wed, 13 May 2026 16:59:00 -0400 Subject: [PATCH] Tweak markdown formatting, fix a few errors --- doc/pg_clickhouse.md | 53 ++++++++++++++++++++++---------------------- 1 file changed, 26 insertions(+), 27 deletions(-) diff --git a/doc/pg_clickhouse.md b/doc/pg_clickhouse.md index ff927ea..b09d51d 100644 --- a/doc/pg_clickhouse.md +++ b/doc/pg_clickhouse.md @@ -188,7 +188,7 @@ CREATE USER MAPPING FOR CURRENT_USER SERVER taxi_srv OPTIONS (user 'demo'); ``` -The The supported options are: +The supported options are: * `user`: The name of the ClickHouse user. Defaults to "default". * `password`: The password of the ClickHouse user. @@ -691,7 +691,7 @@ pg_clickhouse parameters before executing queries that depend on them. ### SET -Use [SET] to set the the pg_clickhouse custom configuration parameters. +Use [SET] to set the pg_clickhouse custom configuration parameters. #### `pg_clickhouse.session_settings` @@ -1288,15 +1288,12 @@ Ranking functions (`row_number`, `rank`, `dense_rank`, `ntile`, `cume_dist`, `percent_rank`) omit their frame clause during pushdown because ClickHouse rejects frame specifications on these functions. - [window functions]: https://www.postgresql.org/docs/current/functions-window.html - "PostgreSQL Docs: Window Functions" - ## Compatibility Notes ### Regular Expressions While pg_clickhouse pushes down regular expressions to ClickHouse equivalents -when [pg_clickhouse.pushdown_regex](pg_clickhousepushdown_regex) is true (the +when [pg_clickhouse.pushdown_regex](#pg_clickhousepushdown_regex) is true (the default), and makes an effort to ensure a basic level of compatibility, be aware of the differences between the two and how pg_clickhouse handles them. @@ -1328,14 +1325,14 @@ aware of the differences between the two and how pg_clickhouse handles them. * The only flags both support, and therefore can be used when evaluated by ClickHouse, are: - RE2 supports only these flags; don't use any other [Postgres flags] - * `i`: case-insensitive * `m`: multi-line mode: * `s`: let `.` match `\n` * `p`: partial newline-sensitive matching (treated the same as `s`) * `t`: tight syntax (the default, removed by pg_clickhouse) + RE2 supports only these flags; don't use any other [Postgres flags] + * Any other flags passed to regular expression functions will cause the function not to be pushed down. @@ -1349,12 +1346,12 @@ aware of the differences between the two and how pg_clickhouse handles them. ClickHouse. To avoid all ambiguity, consider setting -[pg_clickhouse.pushdown_regex](pg_clickhousepushdown_regex) to prevent +[pg_clickhouse.pushdown_regex](#pg_clickhousepushdown_regex) to prevent Postgres regular expression from pushing down to ClickHouse, and using the -[re2 extension], for which pg_clickhouse supports [direct pushdown](#re2) -of ClickHouse-compatible [RE2] regular expressions. +[re2 extension], for which pg_clickhouse supports [direct pushdown](#re2) of +ClickHouse-compatible [RE2] regular expressions. -### to_char() +### `to_char()` PostgreSQL [`to_char()`] for `timestamp` and `timestamp with time zone` pushes down to ClickHouse [formatDateTime] only when the format argument @@ -1370,21 +1367,21 @@ formats date-time values. #### Translated keywords -| PostgreSQL | ClickHouse | Meaning | -| ---------- | ---------- | ------- | -| `YYYY`, `yyyy` | `%Y` | 4-digit year | -| `YY`, `yy` | `%y` | 2-digit year | -| `MM`, `mm` | `%m` | zero-padded month (01–12) | -| `DD`, `dd` | `%d` | zero-padded day of month (01–31) | -| `DDD`, `ddd` | `%j` | zero-padded day of year (001–366) | -| `HH24`, `hh24` | `%H` | zero-padded 24-hour (00–23) | -| `HH`, `hh`, `HH12`, `hh12` | `%I` | zero-padded 12-hour (01–12) | -| `MI`, `mi` | `%i` | zero-padded minute (00–59) | -| `SS`, `ss` | `%S` | zero-padded second (00–59) | -| `Q`, `q` | `%Q` | quarter (1–4) | -| `Mon` | `%b` | abbreviated month name, e.g., `Oct` | -| `Dy` | `%a` | abbreviated weekday name, e.g., `Mon` | -| `AM`, `PM` | `%p` | meridiem indicator, always uppercase | +| PostgreSQL | ClickHouse | Meaning | +| -------------------------- | ---------- | ------------------------------------- | +| `YYYY`, `yyyy` | `%Y` | 4-digit year | +| `YY`, `yy` | `%y` | 2-digit year | +| `MM`, `mm` | `%m` | zero-padded month (01–12) | +| `DD`, `dd` | `%d` | zero-padded day of month (01–31) | +| `DDD`, `ddd` | `%j` | zero-padded day of year (001–366) | +| `HH24`, `hh24` | `%H` | zero-padded 24-hour (00–23) | +| `HH`, `hh`, `HH12`, `hh12` | `%I` | zero-padded 12-hour (01–12) | +| `MI`, `mi` | `%i` | zero-padded minute (00–59) | +| `SS`, `ss` | `%S` | zero-padded second (00–59) | +| `Q`, `q` | `%Q` | quarter (1–4) | +| `Mon` | `%b` | abbreviated month name, e.g., `Oct` | +| `Dy` | `%a` | abbreviated weekday name, e.g., `Mon` | +| `AM`, `PM` | `%p` | meridiem indicator, always uppercase | #### Quoted text and literals @@ -1492,6 +1489,8 @@ Copyright (c) 2025-2026, ClickHouse. "ClickHouse Docs: String" [TEXT]: https://www.postgresql.org/docs/current/datatype-character.html "PostgreSQL Docs: Character Types" + [window functions]: https://www.postgresql.org/docs/current/functions-window.html + "PostgreSQL Docs: Window Functions" [POSIX Regular Expressions]: https://www.postgresql.org/docs/18/functions-matching.html#FUNCTIONS-POSIX-REGEXP "PostgreSQL Docs: POSIX Regular Expressions" [Postgres flags]: https://www.postgresql.org/docs/18/functions-matching.html#POSIX-EMBEDDED-OPTIONS-TABLE