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https://issues.apache.org/jira/browse/SPARK-29034?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dongjoon Hyun updated SPARK-29034:
----------------------------------
Affects Version/s: (was: 3.0.0)
3.1.0
> String Constants with C-style Escapes
> -------------------------------------
>
> Key: SPARK-29034
> URL: https://issues.apache.org/jira/browse/SPARK-29034
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.1.0
> Reporter: Yuming Wang
> Priority: Major
>
> PostgreSQL also accepts "escape" string constants, which are an extension to
> the SQL standard. An escape string constant is specified by writing the
> letter {{E}} (upper or lower case) just before the opening single quote,
> e.g., {{E'foo'}}. (When continuing an escape string constant across lines,
> write {{E}} only before the first opening quote.) Within an escape string, a
> backslash character ({{\}}) begins a C-like _backslash escape_ sequence, in
> which the combination of backslash and following character(s) represent a
> special byte value, as shown in [Table
> 4-1|https://www.postgresql.org/docs/9.3/sql-syntax-lexical.html#SQL-BACKSLASH-TABLE].
> *Table 4-1. Backslash Escape Sequences*
> ||Backslash Escape Sequence||Interpretation||
> |{{\b}}|backspace|
> |{{\f}}|form feed|
> |{{\n}}|newline|
> |{{\r}}|carriage return|
> |{{\t}}|tab|
> |{{\}}{{o}}, {{\}}{{oo}}, {{\}}{{ooo}} ({{o}} = 0 - 7)|octal byte value|
> |{{\x}}{{h}}, {{\x}}{{hh}} ({{h}} = 0 - 9, A - F)|hexadecimal byte value|
> |{{\u}}{{xxxx}}, {{\U}}{{xxxxxxxx}} ({{x}} = 0 - 9, A - F)|16 or 32-bit
> hexadecimal Unicode character value|
> Any other character following a backslash is taken literally. Thus, to
> include a backslash character, write two backslashes ({{\\}}). Also, a single
> quote can be included in an escape string by writing {{\'}}, in addition to
> the normal way of {{''}}.
> It is your responsibility that the byte sequences you create, especially when
> using the octal or hexadecimal escapes, compose valid characters in the
> server character set encoding. When the server encoding is UTF-8, then the
> Unicode escapes or the alternative Unicode escape syntax, explained in
> [Section
> 4.1.2.3|https://www.postgresql.org/docs/9.3/sql-syntax-lexical.html#SQL-SYNTAX-STRINGS-UESCAPE],
> should be used instead. (The alternative would be doing the UTF-8 encoding
> by hand and writing out the bytes, which would be very cumbersome.)
> The Unicode escape syntax works fully only when the server encoding is
> {{UTF8}}. When other server encodings are used, only code points in the ASCII
> range (up to {{\u007F}}) can be specified. Both the 4-digit and the 8-digit
> form can be used to specify UTF-16 surrogate pairs to compose characters with
> code points larger than U+FFFF, although the availability of the 8-digit form
> technically makes this unnecessary. (When surrogate pairs are used when the
> server encoding is {{UTF8}}, they are first combined into a single code point
> that is then encoded in UTF-8.)
>
>
> [https://www.postgresql.org/docs/11/sql-syntax-lexical.html#SQL-BACKSLASH-TABLE]
>
> Example:
> {code:sql}
> postgres=# SET bytea_output TO escape;
> SET
> postgres=# SELECT E'Th\\000omas'::bytea;
> bytea
> ------------
> Th\000omas
> (1 row)
> postgres=# SELECT 'Th\\000omas'::bytea;
> bytea
> -------------
> Th\\000omas
> (1 row)
> {code}
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