Processing and Analytics Vasiliki (Vasia) Kalavri
 vkalavri@bu.edu Spring 2020 4/23: Cardinality and frequency estimation ??? Vasiliki Kalavri | Boston University 2020 Counting distinct elements 2 University 2020 LogLog algorithm Input: stream S, array of m counters, hash fiction h Output: cardinality of S for j=0 to m-1 do: COUNT[j] = 0 for x in S do: i = h(x) j = getLeftBits(i, p) r = Boston University 2020 26 • Query approximation error • Error probability Guarantee: The estimation error for frequencies will not exceed with probability • A higher number of hash functions

.........................................................................1327 49.6. Index Cost Estimation Functions...............................................................................1328 50 ...............................................................................1346 54.1. Row Estimation Examples...................................................................................... shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The default is 128 megabytes (128MB). 17.6.3. Genetic Query Optimizer geqo (boolean)

.........................................................................1219 48.6. Index Cost Estimation Functions...............................................................................1220 49 ...............................................................................1236 52.1. Row Estimation Examples...................................................................................... shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The value is measured in disk pages, which are normally 8192 bytes each. The default

.........................................................................1212 48.6. Index Cost Estimation Functions...............................................................................1213 49 ...............................................................................1229 52.1. Row Estimation Examples...................................................................................... shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The value is measured in disk pages, which are normally 8192 bytes each. The default

.........................................................................1327 49.6. Index Cost Estimation Functions...............................................................................1328 50 ...............................................................................1346 54.1. Row Estimation Examples...................................................................................... shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The default is 128 megabytes (128MB). 17.6.3. Genetic Query Optimizer geqo (boolean)

.........................................................................2077 55.6. Index Cost Estimation Functions...............................................................................2078 56 ...............................................................................2122 61.1. Row Estimation Examples...................................................................................... Options .......................................................................2411 F.32.1.3. Cost Estimation Options...................................................................2412 xli F.32.1.4.

.........................................................................2200 58.6. Index Cost Estimation Functions...............................................................................2201 59 ...............................................................................2252 65.1. Row Estimation Examples...................................................................................... Options .......................................................................2548 F.31.1.3. Cost Estimation Options...................................................................2549 F.31.1.4. Updatability

.........................................................................1475 50.6. Index Cost Estimation Functions...............................................................................1476 51 ...............................................................................1495 55.1. Row Estimation Examples...................................................................................... shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The default is 128 megabytes (128MB). 18.6.3. Genetic Query Optimizer geqo (boolean)

.........................................................................1389 50.6. Index Cost Estimation Functions........................................................................1390 xxiv 51 ...............................................................................1409 55.1. Row Estimation Examples..................................................................................1409 shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The default is 128 megabytes (128MB). 363 Chapter 18. Server Configuration 18.6.3

..........................................................................1050 47. Index Cost Estimation Functions ....................................................................................1051 shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The value is measured in disk pages, which are normally 8192 bytes each. The default num can be a literal integer or a host variable containing an integer. Possible fields are: CARDINALITY (integer) number of rows in the result set DATA actual data item (therefore, the data type of