6. A system for determining query plans comprising: a processor that: obtains a current query; parses the current query into a first parameterized literal and a first signature key; determines that the first signature key matches a second signature key stored in a hash table; obtains a literals data structure from the hash table corresponding to the second signature key, the literals data structure comprising a group of literals, a parameterization indicator, and a statistical histogram for each parameterized literal in the group of literals, each statistical histogram comprising a list of intervals defined by a low bound and a high bound; identifies, using the parameterization indicator, a second parameterized literal in the group of literals; determines that the first parameterized literal is contained in a range defined by the low bound and the high bound of the statistical histogram for the second parameterized literal; obtains a stored query plan for the second signature key; and executes the query plan on the current query.
6. A system for determining query plans comprising: a processor that: obtains a current query; parses the current query into a first parameterized literal and a first signature key; determines that the first signature key matches a second signature key stored in a hash table; obtains a literals data structure from the hash table corresponding to the second signature key, the literals data structure comprising a group of literals, a parameterization indicator, and a statistical histogram for each parameterized literal in the group of literals, each statistical histogram comprising a list of intervals defined by a low bound and a high bound; identifies, using the parameterization indicator, a second parameterized literal in the group of literals; determines that the first parameterized literal is contained in a range defined by the low bound and the high bound of the statistical histogram for the second parameterized literal; obtains a stored query plan for the second signature key; and executes the query plan on the current query. 9. The system of claim 6 wherein the literals data structure further comprises a query plan key and the processor obtains the stored query plan for the second signature key using the query plan key.