sql: support expressions as ON CONFLICT targets #67893
Description
We don't currently support expressions as ON CONFLICT targets. This means that unique expression indexes (still a WIP at the time this was written) cannot be selected as arbiters for INSERT .. ON CONFLICT statements. This will require adding support for expression ON CONFLICT targets to the parser and the AST, and updating optbuilder's arbiter logic to select arbiters based on the expression.
Example:
defaultdb> SET experimental_enable_expression_indexes=true;
SET
defaultdb> CREATE TABLE t (a INT, b INT, UNIQUE INDEX ((a + b)));
CREATE TABLE
defaultdb> INSERT INTO t VALUES (1, 2) ON CONFLICT ((a + b)) DO NOTHING;
invalid syntax: statement ignored: at or near "(": syntax error
SQLSTATE: 42601
DETAIL: source SQL:
INSERT INTO t VALUES (1, 2) ON CONFLICT ((a + b)) DO NOTHING
^
HINT: try \h INSERT
defaultdb> INSERT INTO t VALUES (1, 2) ON CONFLICT ((a + b)) DO UPDATE SET a = 10;
invalid syntax: statement ignored: at or near "(": syntax error
SQLSTATE: 42601
DETAIL: source SQL:
INSERT INTO t VALUES (1, 2) ON CONFLICT ((a + b)) DO UPDATE SET a = 10
^
HINT: try \h INSERT
Jira issue: CRDB-8765