Selected index for a constraint by Oracle when there are two posible choices
I cannot understand why Oracle select an index for a constraint, the test case is:
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CREATE TABLE testtts."PR_PRICETYPECODELNG"
("PR_PRICETYPECODEID" VARCHAR2(10 CHAR) NOT NULL ENABLE,
"LANGUAGECODE" VARCHAR2(2 CHAR) NOT NULL ENABLE,
"NAME" VARCHAR2(100 CHAR) NOT NULL ENABLE,
"DESCRIPTION" VARCHAR2(100 CHAR),
"VERSION" NUMBER(4,0) DEFAULT 0 NOT NULL ENABLE,
"AU_USERIDINS" NUMBER,
"INSERTDATE" DATE,
"AU_USERIDUPD" NUMBER,
"MODIFYDATE" DATE,
"DBUSERINS" VARCHAR2(30 BYTE),
"DBUSERUPD" VARCHAR2(30 BYTE),
CONSTRAINT "PR_PRICETYPECODELNG_LNGCODE_FK" FOREIGN KEY ("LANGUAGECODE")
REFERENCES TESTTTS."ISO_LANGUAGE" ("LANGUAGECODE") DEFERRABLE INITIALLY DEFERRED ENABLE,
CONSTRAINT "PR_PRICETYPECODELNG_FK" FOREIGN KEY ("PR_PRICETYPECODEID")
REFERENCES TESTTTS."PR_PRICETYPECODE" ("PR_PRICETYPECODEID") DEFERRABLE INITIALLY DEFERRED ENABLE)