15 citations · 44 across the 9 of their papers we have counts for
10 papers · 1 filter
The Importance of Parameters in Ranking Functions
Christoph Standke, Nikolaos Tziavelis, Wolfgang Gatterbauer +1
How important is the weight of a given column in determining the ranking of tuples in a table? To address such an explanation question about a ranking function, we investigate the…
Database Theory in Action: Direct Access to Query Answers
Jiayin Hu, Nikolaos Tziavelis
Direct access asks for the retrieval of query answers by their ranked position, given a query and a desired order. While the time complexity of data structures supporting such acce…
Fine-Grained Dichotomies for Conjunctive Queries with Minimum or Maximum
Nofar Carmeli, Nikolaos Tziavelis
We investigate the fine-grained complexity of direct access to Conjunctive Query (CQ) answers according to their position, ordered by the minimum (or maximum) value between attribu…
Ranked Enumeration for Database Queries
Nikolaos Tziavelis, Wolfgang Gatterbauer, Mirek Riedewald
Ranked enumeration is a query-answering paradigm where the query answers are returned incrementally in order of importance (instead of returning all answers at once). Importance is…
Efficient Computation of Quantiles over Joins
Nikolaos Tziavelis, Nofar Carmeli, Wolfgang Gatterbauer +2
We present efficient algorithms for Quantile Join Queries, abbreviated as %JQ. A %JQ asks for the answer at a specified relative position (e.g., 50% for the median) under some orde…
Any-k Algorithms for Enumerating Ranked Answers to Conjunctive Queries
Nikolaos Tziavelis, Wolfgang Gatterbauer, Mirek Riedewald
We study ranked enumeration for Conjunctive Queries (CQs) where the answers are ordered by a given ranking function (e.g., an ORDER BY clause in SQL). We develop "any-k" algorithms…
Beyond Equi-joins: Ranking, Enumeration and Factorization
Nikolaos Tziavelis, Wolfgang Gatterbauer, Mirek Riedewald
We study theta-joins in general and join predicates with conjunctions and disjunctions of inequalities in particular, focusing on ranked enumeration where the answers are returned…
Tractable Orders for Direct Access to Ranked Answers of Conjunctive Queries
Nofar Carmeli, Nikolaos Tziavelis, Wolfgang Gatterbauer +2
We study the question of when we can provide direct access to the k-th answer to a Conjunctive Query (CQ) according to a specified order over the answers in time logarithmic in the…
Optimal Join Algorithms Meet Top-k
Nikolaos Tziavelis, Wolfgang Gatterbauer, Mirek Riedewald
Top-k queries have been studied intensively in the database community and they are an important means to reduce query cost when only the "best" or "most interesting" results are ne…
Optimal Algorithms for Ranked Enumeration of Answers to Full Conjunctive Queries
Nikolaos Tziavelis, Deepak Ajwani, Wolfgang Gatterbauer +2
We study ranked enumeration of join-query results according to very general orders defined by selective dioids. Our main contribution is a framework for ranked enumeration over a c…