Sampling-Based Query Re-Optimization

Despite of decades of work, query optimizers still make mistakes on "difficult" queries because of bad cardinality estimates, often due to the interaction of multiple predicates and correlations in the data. In this paper, we propose a low-cost post-processing step that can take a plan produced by the optimizer, detect when it is likely to have made such a mistake, and take steps to fix it. Specifically, our solution is a sampling-based iterative procedure that requires almost no changes to the original query optimizer or query evaluation mechanism of the system. We show that this indeed imposes low overhead and catches cases where three widely used optimizers (PostgreSQL and two commercial systems) make large errors.Comment: This is the extended version of a paper with the same title and authors that appears in the Proceedings of the ACM SIGMOD International Conference on Management of Data (SIGMOD 2016

Radiation and Chemical Reaction Effects on Unsteady MHD Free Convective Periodic Heat Transport Modeling In a Saturated Porous Medium for Arotating System

A rotating model is extended for a two-dimensional, unsteady, incompressible electrically conducting, laminar immediate convection boundary layer flow of light and mass communicate in a saturated porous crystal ball gazer, among an overall vertical porous surface in the perseverance of radiation and vicious circle effects was considered. The fundamental equations governing the flow are in the art an element of partial differential equations and have been reduced to a inhere of non-linear ordinary differential equations by applying suitable similarity transformations. The problem is tackled analytically using classical two term perturbation technique. Pertinent results with respect to embedded parameters are displayed through graphically for the velocity, Temperature, concentration, skin friction, Sherwood number, Nusselt number are discussed qualitatively

Experimental Evidence of Time Delay Induced Death in Coupled Limit Cycle Oscillators

Experimental observations of time delay induced amplitude death in a pair of coupled nonlinear electronic circuits that are individually capable of exhibiting limit cycle oscillations are described. In particular, the existence of multiply connected death islands in the parameter space of the coupling strength and the time delay parameter for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds in [Phys. Rev. Lett. 80, 5109 (1998); Physica 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay and the onset of both in-phase and anti-phase collective oscillations.Comment: 4 aps formatted RevTeX pages; 6 figures; to appear in Phys. Rev. Let

Effect of an electric field on superfluid helium scintillation produced by alpha-particle sources

We report a study of the intensity and time dependence of scintillation produced by weak alpha particle sources in superfluid helium in the presence of an electric field (0 - 45 kV/cm) in the temperature range of 0.2 K to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric field strength with a reduction of 15% at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to the conclusion that roughly 40% of the scintillation results from species formed from atoms originally promoted to excited states and 60% from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the alpha track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.Comment: 17 pages, 23 figure

A Case For Induced Mutation In Chickpea For Ascochyta Blight Resistance

Chickpea (Cicer aria tin at L.) is an important grain leguae grown in several coiaitries. Blight caused by Ascochyta rebiol (Pass] Labrousse Is widespread and results In considerable losses in several countries (2, 5, S, 8, 11, 12, 14, IS, 17, 19, 22, 26, 29, 30, 51, 33, 35, 36, 38, and 40). Extensive efforts have been aade by earlier workers to identify resistance sources and aaniadxe losses through the development of resistant/tolerant varieties (1, 4, 6, 7, 9, 13, 16, 20 21, 23, 2S, 28, 34, 36, and 38). Host of the screening work has been carried out in fields, either in areas where natural epiphytotics occur or through artificial field inoculations in areas where the disease is not always severe (13, 16, 24, 25, 32, and 37)

Influence of sterility mosaic resistant pigeonpeas on multiplication of the mite vector

Pigeonpea lines resistant to the causal agent of sterility mosaic did not permit continued multiplication of its eriophyid mite vector, Aceria cajani. Resistance to the causal agent and lack -of continued multiplication of the mite vector on these lines are expected to provide greater stability of resistance to the disease...

Preliminary information on chickpea stunt

The name chickpea stunt is introduced for a disease of Cicer arietinum that is described from Andhra Pradesh, and occurs at various other places in India, and in Turkey and Iran. Attempts to transmit the causal agent through sap, graft and dodder failed, but it was repeatedly transmitted in the laboratory by the aphid Aphis craccivora Koch. After acquisition feeding periods of from 0.5 h to 4 days and inoculation feeding periods of 48 h, symptoms developed in test plants after 20-45 days, the success in transmission varying from 25 to 80%.ADDITIONAL ABSTRACT:A condition in chickpeas called 'wilt complex' and now named chickpea stunt, prevalent in central and N. India, caused fewer pods to develop/plant and a reduction in seed yield of up to 80%/infected plant. Possible causes of chickpea stunt are discussed; it can be transmitted by Aphis craccivor

New Spectroscopic Observations of the Post-AGB Star V354Lac=IRAS22272+5435

The strongest absorption features with the lower-level excitation potentials $\chi_{\rm low}<1$ eV are found to be split in the high-resolution optical spectra of the post-AGB star V354 Lac taken in 2007--2008. Main parameters, T$_{eff}$=5650 K, $\log g$=0.2, $\xi_t$=5.0 km/s, and the abundances of 22 chemical elements in the star's atmosphere are found. The overabundance of the $s$-process chemical elements (Ba, La, Ce, Nd) in the star's atmosphere is partly due to the splitting of strong lines of the ions of these metals. The peculiarities of the spectrum in the wavelength interval containing the LiI $\lambda$ 6707 \AA{} line can be naturally explained only by taking the overabundances of the CeII and SmII heavy-metal ions into account. The best agreement with the synthetic spectrum is achieved assuming $\epsilon$(LiI)=2.0, $\epsilon$(CeII)=3.2, and $\epsilon$(SmII)=2.7. The velocity field both in the atmosphere and in the circumstellar envelope of V354 Lac remained stationary throughout the last 15 years of our observations.Comment: 16 pages, 6 figures, 2 table