several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “suc- cessful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “success- ful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “suc- cessful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “suc- cessful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “suc- cessful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “success- ful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “success- ful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11.3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “success- ful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11-3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “successful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible

several principles in mind: • Implicit conversions should never have surprising or unpredictable outcomes. • There should be no extra overhead in the parser or executor if a query does not need implicit Example 11-3. Setting up a Partial Unique Index Suppose that we have a table describing test outcomes. We wish to ensure that there is only one “success- ful” entry for a given subject and target combination for insertion will either insert or update. Unless there are unrelated errors, one of those two outcomes is guaranteed. If a conflict originates in another transaction whose effects are not yet visible