Usability improvements for secondary indices.

[alexey-milovidov]

Use case
People usually create indices of type set with unlimited size. It will lead to troubles.
Other common mistake is to specify high GRANULARITY of secondary index.

Describe the solution you'd like

1. set(0) should be default value from merge-tree setting (for example, 100).
2. If GRANULARITY of secondary index is greater than some merge-tree setting (for example, 1000), throw an exception.

Always allow to ATTACH table.

[zhang2014]

For different indexes: set different default values for granularity may also be helpful?

[alexey-milovidov]

For different indexes: set different default values for granularity may also be helpful?

Usually granularity 1 is enough and bigger value is considered as fine-tuning.

[tobia]

Why does set(0) lead to trouble?