For this article, explaining this one restriction will suffice. Depending on the index selected, choose the predicates to push down, see the query is covered or not, decide on sort and pagination strategy.Ĭonsider the case of MongoDB restriction." A collection can have at most one text index." It documents a few other restrictions along with this.Selecting the optimal index(es) for each of the table (keyspaces in Couchbase N1QL, collection in case of MongoDB).Query rewrite based on heuristics, cost or both.At a very high level, SQL optimizers decide the following before creating the execution tree: Database OptimizerĪ query optimizer chooses an optimal index and access paths to execute the query. When you don't have a good optimizer, developers have to live with feature restrictions and DBAs have to live with performance issues. Now, most NoSQL databases have SQL-like query language support. The cost of Memory, CPU, disk usage is added to the cost of a plan in a cost-based optimizer. Efficiency is measured in latency and throughput, depending on the workload. The Query optimizer evaluates the possibilities and selects the efficient plan. Queries can be executed in many different ways. The next day, when he told his wife he's going to the corner store, she asked him, "Are you taking the short route or the long one?" A man returned home after walking around the globe for eleven years.
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