27da1a796f
We try to use the pager only when more than a screenful's worth of data is to be printed. However, the code in print.c that's concerned with counting the number of lines that will be needed missed a lot of edge cases: * While plain aligned mode accounted for embedded newlines in column headers and table cells, unaligned and vertical output modes did not. * In particular, since vertical mode repeats the headers for each record, we need to account for embedded newlines in the headers for each record. * Multi-line table titles were not accounted for. * tuples_only mode (where headers aren't printed) wasn't accounted for. * Footers were accounted for as one line per footer, again missing the possibility of multi-line footers. (In some cases such as "\d+" on a view, there can be many lines in a footer.) Also, we failed to account for the default footer. To fix, move the entire responsibility for counting lines into IsPagerNeeded (or actually, into a new subroutine count_table_lines), and then expand the logic as appropriate. Also restructure to make it perhaps a bit easier to follow. It's still only completely accurate for ALIGNED/WRAPPED/UNALIGNED formats, but the other formats are not typically used with interactive output. Arrange to not run count_table_lines at all unless we will use its result, and teach it to quit early as soon as it's proven that the output is long enough to require use of the pager. When dealing with large tables this should save a noticeable amount of time, since pg_wcssize() isn't exactly cheap. In passing, move the "flog" output step to the bottom of printTable(), rather than running it when we've already opened the pager in some modes. In principle it shouldn't interfere with the pager because flog should always point to a non-interactive file; but it seems silly to risk any interference, especially when the existing positioning seems to have been chosen with the aid of a dartboard. Also add a TAP test to exercise pager mode. Up to now, we have had zero test coverage of these code paths, because they aren't reached unless isatty(stdout). We do have the test infrastructure to improve that situation, though. Following the lead of 010_tab_completion.pl, set up an interactive psql and feed it some test cases. To detect whether it really did invoke the pager, point PSQL_PAGER to "wc -l". The test is skipped if that utility isn't available. Author: Erik Wienhold <ewie@ewie.name> Test-authored-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/2dd2430f-dd20-4c89-97fd-242616a3d768@ewie.name
PostgreSQL Database Management System
This directory contains the source code distribution of the PostgreSQL database management system.
PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings.
Copyright and license information can be found in the file COPYRIGHT.
General documentation about this version of PostgreSQL can be found at https://www.postgresql.org/docs/devel/. In particular, information about building PostgreSQL from the source code can be found at https://www.postgresql.org/docs/devel/installation.html.
The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.