Smart auto-indexing

[jqnatividad]

Have an env var named QSV_AUTOINDEX.

It will be a string with three positions - PUI:

• When P (for Primary Key) is 1, automatically create a primary key for a column with cardinality=rowcount, and there is no other column with cardinality=rowcount.
• When U (for Unique Index) is 1, create a unique index for ALL columns where cardinality=rowcount.
• When I (Index) is not zero, create an index for columns that have cardinality >= I.

[jqnatividad]

This is implemented as follows:

# if AUTO_INDEX_THRESHOLD > 0 or AUTO_INDEX_DATES is true
# create indices automatically based on summary statistics
# For columns w/ cardinality = record_count, it's all unique values, create a unique index
# If AUTO_INDEX_DATES is true, index all date columns
# if a column's cardinality <= AUTO_INDEX_THRESHOLD, create an index for that column