1. A method for obtaining information about a subsurface formation from acoustic signals that contain information about the subsurface formation, comprising:
a) providing a plurality of received optical signals resulting from the transmission of an optical signal into a fiber optic cable that includes a sensing apparatus comprising a plurality of substantially parallel fiber lengths whereby each received optical signal comprises a portion of the optical signal that has been backscattered from a segment of a different fiber length;
b) processing the received optical signals from the segments of the different fiber lengths so as to effectively align the segments with one location of interest along the sensing apparatus before proceeding to step c), wherein the different segments together correspond to a single selected location along the sensing apparatus; and
c) on a processor, processing the received optical signals so as to obtain information about an acoustic signal received at the different segments there by obtaining practically simultaneous multiple detections by the different segments of the acoustic signals at the single selected location along the sensing apparatus.
2. The method according to claim 1 wherein the sensing apparatus comprises a ribbon cable comprising a plurality of fibers.
3. The method according to claim 2 wherein the plurality of substantially parallel fibers are connected in series so as to form one long fiber.
4. The method according to claim 1 wherein the lateral distance between the different segments is less than 10 meters.
5. The method according to claim 1 wherein the sensing apparatus comprises a single cable that is folded so as to form a plurality of substantially parallel cable lengths, wherein the lateral distance between interrogated fiber segments is less than 10 cm.
6. The method according to claim 1 wherein the sensing apparatus comprises a plurality of substantially parallel cable lengths wherein at least one fiber in each of said cable lengths is connected to a fiber an adjacent cable lengths so as to form one long fiber.
7. The method according to claim 1 wherein step c) includes processing the collected optical signals so as to generate seismic traces comprising one seismic trace for each of the different segments at the single selected location along the sensing apparatus, and stacking the seismic traces.
8. The method according to claim 1 wherein each segment is less than 10 m long.
9. The method according to claim 1, wherein the substantially parallel fiber lengths lie within 2 meters of each other.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A join execution method executed by a join query execution device for searching an external data source connected to a data management system by means of a table function and executing joining processing against a join query regarding a search result of the table function and a table managed by the data management system, wherein the join execution method comprising:
a first step, executed by the join query execution device, of executing the joining processing regarding the search result of the table function and the table managed by the data management system by a first joining method;
a second step, executed by the join query execution device, of determining whether the first joining method is an appropriate joining method as a joining method for the joining processing or not, by using information acquired by search processing on the external data source by means of the table function andor information found during the joining processing; and
a third step, executed by the join query execution device, of regarding, in case it is determined that the first joining method is not the appropriate joining method as the joining method for the joining processing, a second joining method as the faster than the first joining method and switching the joining method for the joining processing from the first joining method to the second joining method.
2. The join query execution method according to claim 1,
wherein in the first step, the join query execution device executes the joining processing and the search processing on the external data source by means of the table function in parallel.
3. The join query execution method according to claim 1,
wherein the first joining method is a Nested-Loop joining method and the second joining method is a Hash joining method.
4. The join query execution method according to claim 1,
wherein in the second step, in case a search result count of the search processing can be acquired upon execution of the search processing on the external data source, the join query execution device acquires the search result count and determines whether the first joining method is the appropriate joining method as the joining method for the joining processing or not, by using the acquired search result count and the information found during the joining processing; and
wherein in the second step, when the search result count of the search processing cannot be acquired upon execution of the search processing on the external data source, the join query execution device determines whether the first joining method is the appropriate joining method as the joining method for the joining processing or not, by using only the information found during the joining processing.
5. The join query execution method according to claim 4,
wherein in the second step, when the search result count of the search processing can be acquired upon execution of the search processing on the external data source,
the join query execution device:
acquires the search result count;
calculates a progress of the joining processing and remaining quantity of the joining processing by using the search result count of the external data source every time the joining processing is executed on one search result of the external data source and the table managed by the data management system; and
determines whether the Nested-Loop joining method is the appropriate joining method as the joining method for the joining processing or not, by comparing the found progress and remaining quantity of the joining processing with a first threshold which is predetermined for the progress and the remaining quantity, respectively.
6. The join query execution method according to claim 5,
wherein the join query execution device calculates the progress of the joining processing by dividing the number of pieces of data, on which the joining processing has already been executed, among the search result of the external data source, by the search result count of the external data source.
7. The join query execution method according to claim 5,
wherein the join query execution device calculates the remaining quantity of the joining processing by subtracting the number of pieces of data, on which the joining processing has already been executed, from the search result count of the external data source.
8. The join query execution method according to claim 4,
wherein in the second step, when the search result count of the search processing can be acquired upon execution of the search processing on the external data source,
the join query execution device:
acquires the search result count;
calculates the progress of the joining processing by using the search result count of the external data source every time the joining processing is executed on one search result of the external data source and the table managed by the data management system; and calculates a hit rate that is a rate of data, which satisfy a joining condition, among entire data of the table for the one search result of the external data source on which the joining processing has been executed; and
determines whether the first joining method is the appropriate joining method as the joining method for the joining processing or not, by comparing the found progress of the joining processing and the hit rate with a second threshold which is predetermined for the progress and the hit rate, respectively.
9. The join query execution method according to claim 8,
wherein the join query execution device calculates the progress of the joining processing by dividing the number of pieces of data, on which the joining processing has already been executed, among the search result of the external data source, by the search result count of the external data source.
10. The join query execution method according to claim 4,
wherein when the search result count of the search processing cannot be acquired upon execution of the search processing on the external data source,
the join query execution device:
calculates remaining quantity of the joining processing every time the joining processing is executed on one search result of the external data source and the table managed by the data management system; and
determines whether the first joining method is the appropriate joining method as the joining method for the joining processing or not, by comparing the found remaining quantity of the joining processing with a third threshold which is predetermined for the remaining quantity.
11. The join query execution method according to claim 10,
wherein the join query execution device calculates the remaining quantity of the joining processing by subtracting the number of pieces of data, on which the joining processing has already been executed, from the search result count of the external data source.
12. The join query execution method according to claim 1,
wherein when it is determined in the second step that the first joining method is the appropriate joining method, the join query execution device executes the joining processing by the first joining method in the third step; and
wherein, in the second step, in case it is determined that the first joining method is not the appropriate joining method, the join query execution device switches the joining method to the second joining method in order to execute the joining processing regarding the search result on which the joining method has not been executed by the second joining method in the third step.
13. A join query execution device for searching an external data source connected to a data management system by means of a table function and executing joining processing against a join query regarding a search result of the table function and a table managed by the data management system,
the join query execution device comprising:
a table function unit that searches the external data source by issuing a search request to the external data source;
a joining execution unit that executes the joining processing regarding the search result of the table function and the table managed by the data management system by a first joining method or a second joining method whose processing speed is faster than that of the first joining method;
a switch command unit that determines whether the first joining method is an appropriate joining method as a joining method for the joining processing or not, by using information acquired by search processing on the external data source by the table function unit andor information found during the joining processing, and gives a command to the joining execution unit to switch the joining method for the joining processing to the second joining method when it is determined that the first joining method is not the appropriate joining method as the joining method for the joining processing; and
a control unit that controls activation of the table function unit, the joining execution unit, and the switch command unit.
14. A storage medium storing a program for having a join query execution device search an external data source connected to a data management system by means of a table function and execute joining processing against a join query regarding a search result of the table function and a table managed by the data management system, wherein the processing comprising:
a first step of executing the joining processing regarding the search result of the table function and the table managed by the data management system by a first joining method;
a second step of determining whether the first joining method is an appropriate joining method as a joining method for the joining processing or not, by using information acquired by search processing on the external data source by means of the table function andor information found during the joining processing; and
a third step, which is executed when it is determined that the first joining method is not the appropriate joining method as the joining method for the joining processing, of regarding a second joining method as the faster than the first joining method and switching the joining method for the joining processing from the first joining method to the second joining method.