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sql/parser: unreserve INDEX and NOTHING from the RHS of SET statements #31731

Merged
merged 2 commits into from
Oct 23, 2018
Merged

sql/parser: unreserve INDEX and NOTHING from the RHS of SET statements #31731

merged 2 commits into from
Oct 23, 2018

Commits on Oct 23, 2018

  1. sql/parser: re-allow FAMILY, MINVALUE, MAXVALUE, NOTHING and INDEX in… 

    … table names

CockroachDB introduced non-standard extensions to its SQL dialect very
early in its history, before concerns of compatibility with existing
PostgreSQL clients became a priority. When these features were added,
new keywords were liberally marked as "reserved", so as to "make the
grammar work", and without noticing / care for the fact that this
change would make existing valid SQL queries/clients encounter new
errors.

An example of this:

1. let's make "column families" a thing

2. the syntax `create table(..., constraint xxx family(a,b,c))` is not
   good enough (although this would not require reserved keywords), we
   really want also `create table (..., family (a,b,c))` to be
   possible.

3. oh, the grammar won't let us because "family" is a possible column
   name? No matter! let's mark "FAMILY" as a reserved name for
   column/function names.

   - No concern for the fact that "family" is a  perfectly valid
	 English name for things that people want to make an attribute of
	 in inventory / classification tables.

   - No concern for the fact that reserved column/function names are
	 also reserved for table names.

4. (much later) Clients complaining about the fact they can't call
   their columns or tables `family` without quoting.

Ditto "INDEX", "MINVALUE", "MAXVALUE", and perhaps others.

Moral of the story: DO NOT MAKE NEW RESERVED KEYWORDS UNLESS YOU'RE
VERY VERY VERY SURE THAT THERE IS NO LEGITIMATE USE FOR THEM IN CLIENT
APPS EVER.

(An example perhaps: the word "NOTHING" was also marked as reserved,
but it's much more unlikely this word will ever be used for something
useful.)

This patch restores the use of FAMILY, INDEX, NOTHING, MINVALUE and
MAXVALUE in table and function names, by introducing an awkward dance
in the grammar of keyword non-terminals and database object names.

They remain reserved as colum names because of the non-standard
CockroachDB extensions.

Release note (sql change): It is now again possible to use the
keywords FAMILY, MINVALUE, MAXVALUE, INDEX or NOTHING as table names,
for compatibility with PostgreSQL.
    @knz
    knz committed Oct 23, 2018
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  2. sql/parser: unreserve INDEX and NOTHING from the RHS of SET statements 

    The SET statement in the pg dialect is special because it
auto-converts identifiers on its RHS to symbolic values or strings. In
particular it is meant to support a diversity of special keywords as
pseudo-values.

This patch ensures that INDEX and NOTHING are accepted on the RHS.

Release note (sql change): the names "index" and "nothing" are again
accepted in the right-hand-side of the assignment in SET statements,
for compatibility with PostgreSQL.
    @knz
    knz committed Oct 23, 2018
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