Support WHERE clause in INSERT ... ON CONFLICT

In PostgreSQL the full synopsis for the conflict_action in an INSERT statement is:

and conflict_action is one of:

    DO NOTHING
    DO UPDATE SET { column_name = { expression | DEFAULT } |
                    ( column_name [, ...] ) = [ ROW ] ( { expression | DEFAULT } [, ...] ) |
                    ( column_name [, ...] ) = ( sub-SELECT )
                  } [, ...]
              [ WHERE condition ]

CrateDB does not support WHERE condition.

Example from the PostgreSQL documentation:

-- Don't update existing distributors based in a certain ZIP code
INSERT INTO distributors AS d (did, dname) VALUES (8, 'Anvil Distribution')
    ON CONFLICT (did) DO UPDATE
    SET dname = EXCLUDED.dname || ' (formerly ' || d.dname || ')'
    WHERE d.zipcode <> '21201';

Users could avoid “no-op” updates like the following:

insert into test (a, b) 
values (1, ‘2020-01-01T00:00:00Z’::timestamp)
on conflict (a)
do update set b = case when excluded.b > b then excluded.b else b end;

(This is from https://github.com/crate/crate/issues/9723)

[mfussenegger]

@daminichopra

Yes, this issue is quite involved and touches many parts.

• The parser needs to be extended to support the WHERE clause in ON CONFLICT

  • The grammar is in sql-parser/src/main/antlr/SqlBase.g4, tests are in sql-parser/src/test/java/io/crate/sql/parser/TestStatementBuilder.java. To generate the parser from the grammar you can run ./gradlew :sql-parser:compileJava or ./gradlew :sql-parser:test.
  • visitInsert in sql-parser/src/main/java/io/crate/sql/parser/AstBuilder.java needs to be extended, so that the DuplicateKeyContext receives a where Expression

• sql/src/main/java/io/crate/analyze/InsertAnalyzer.java needs to be extended to analyze the where Expression. The AnalyzedInsertStatement should receive a new property of type Symbol that contains the analyzed expression. Analyzer tests for inserts are in sql/src/test/java/io/crate/analyze/InsertAnalyzerTest.java

• The execution layer needs to be extended in various components. I can give some more pointers if you’d like later. Maybe you could first open up a draft with the parser/analyzer extension and we can guide you further from there?

[daminichopra]

Hi @mfussenegger , if no one is working on this issue then please assign this issue to me. Thank you