Document about the unsupported gin index cases in known issues

[priyanshi-yb]

Issue in some of the gin index type as gin indexes are partially supported by YugabyteDB (yugabyte/yugabyte-db#7850).
For example, Oracle as a sourceDB:
Multi column gin index.
Source Schema -

CREATE TABLE members(
    member_id INT GENERATED BY DEFAULT AS IDENTITY,
    first_name VARCHAR2(100) NOT NULL,
    last_name VARCHAR2(100) NOT NULL,
    gender CHAR(1) NOT NULL,
    dob DATE NOT NULL,
    email VARCHAR2(255) NOT NULL,
    PRIMARY KEY(member_id)
);

CREATE BITMAP INDEX members_gender_bm_index on members(gender,member_id);

Exported Schema -

CREATE TABLE members (
	member_id bigint GENERATED BY DEFAULT AS IDENTITY (START WITH 1 INCREMENT BY 1 MAXVALUE 9223372036854775807 MINVALUE 1 NO CYCLE CACHE 20 ),
	first_name varchar(100) NOT NULL,
	last_name varchar(100) NOT NULL,
	gender char(1) NOT NULL,
	dob timestamp NOT NULL,
	email varchar(255) NOT NULL,
	PRIMARY KEY (member_id)
) ;
CREATE INDEX members_gender_bm_index ON members USING gin(gender, member_id);

Error in import schema -

ERROR: data type character has no default operator class for access method "ybgin" (SQLSTATE 42704)

Workaround is to modify such type of indexes with some supported cases or use other type of indexing as per requirement.

[priyanshi-yb]

Added this in manual review guideline docs, please update the known issues page @aishwarya24. Thanks

[aishwarya24]

Resolved in this PR : yugabyte/yugabyte-db#15758