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## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123. --> - Does not close an issue. - This is targeted toward high fanout repartitions we see in shuffles in distributed-datafusion (datafusion-contrib/datafusion-distributed#385, datafusion-contrib/datafusion-distributed#353). - Related ongoing effort to improve metrics and repartition performance: #21148, #22155. ## Rationale for this change <!-- Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed. Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes. --> Hash repartition currently builds one output batch per non-empty target partition by calling `take_arrays` separately for each partition. At high fanout this means an input batch can issue many take kernels, which shows in repartition-heavy queries. This changes hash repartition to concatenate the per-partition row indices, call `take_arrays` once for the input batch, and then slice the reordered batch back into per-partition output batches. This is complementary to #22010: that PR reduces channel/gate traffic from many small batches, while this PR reduces the Arrow take-kernel work required to create the repartitioned batches. ## What changes are included in this PR? <!-- There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. --> - Replaces per-partition hash repartition `take_arrays` calls with one grouped `take_arrays` call per input batch. - Tracks partition ranges into the grouped reordered batch and returns zero-copy `RecordBatch::slice` outputs for each non-empty partition. How the grouped take works: ```text input rows: 0 1 2 3 4 5 6 partition 0: [2, 5] partition 1: [] partition 2: [0, 3, 4] partition 3: [1, 6] grouped indices: [2, 5, 0, 3, 4, 1, 6] partition ranges: [(0, start=0, len=2), (2, start=2, len=3), (3, start=5, len=2)] take once: rows [2, 5, 0, 3, 4, 1, 6] slice outputs: partition 0 = slice(0, 2) partition 2 = slice(2, 3) partition 3 = slice(5, 2) ``` ## Are these changes tested? <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> - `cargo test -p datafusion-physical-plan repartition --lib` **Benchmarks:** Default TPCH SF10 summary, with no `--batch-size` override: | Partitions | main total ms | grouped total ms | change | wins | losses | biggest win | biggest loss |---:|---:|---:|---:|---:|---:|---:|---:| | 8 | 6234.28 | 6149.98 | -1.35% | 10 | 12 | Q3 -22.12% | Q21 5.47% | | 16 | 5602.63 | 5427.40 | -3.13% | 18 | 4 | Q21 -10.67% | Q10 4.47% | | 32 | 6097.10 | 5738.12 | -5.89% | 20 | 2 | Q8 -10.45% | Q6 0.47% | | 64 | 7194.70 | 6693.30 | -6.97% | 15 | 7 | Q21 -15.92% | Q1 5.02% | | 300 | 26276.60 | 23701.32 | -9.80% | 19 | 3 | Q21 -24.24% | Q1 9.45% | <details> <summary>TPCH SF10 default batch size, 8 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 411.40 | 356.46 | -13.35% | 1.154x | | Q2 | 117.97 | 95.68 | -18.89% | 1.233x | | Q3 | 278.88 | 217.20 | -22.12% | 1.284x | | Q4 | 104.92 | 98.47 | -6.15% | 1.065x | | Q5 | 311.36 | 302.12 | -2.97% | 1.031x | | Q6 | 133.82 | 135.13 | 0.98% | 0.990x | | Q7 | 366.32 | 360.50 | -1.59% | 1.016x | | Q8 | 408.86 | 391.14 | -4.33% | 1.045x | | Q9 | 509.62 | 515.74 | 1.20% | 0.988x | | Q10 | 278.97 | 273.80 | -1.85% | 1.019x | | Q11 | 76.55 | 75.34 | -1.58% | 1.016x | | Q12 | 175.56 | 180.87 | 3.03% | 0.971x | | Q13 | 211.03 | 221.03 | 4.74% | 0.955x | | Q14 | 183.05 | 189.95 | 3.77% | 0.964x | | Q15 | 318.46 | 328.85 | 3.26% | 0.968x | | Q16 | 57.66 | 57.70 | 0.08% | 0.999x | | Q17 | 505.05 | 503.77 | -0.25% | 1.003x | | Q18 | 596.49 | 602.77 | 1.05% | 0.990x | | Q19 | 273.60 | 283.41 | 3.58% | 0.965x | | Q20 | 255.73 | 267.30 | 4.52% | 0.957x | | Q21 | 592.44 | 624.83 | 5.47% | 0.948x | | Q22 | 66.54 | 67.91 | 2.05% | 0.980x | </details> <details> <summary>TPCH SF10 default batch size, 16 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 278.95 | 276.85 | -0.76% | 1.008x | | Q2 | 95.84 | 94.86 | -1.02% | 1.010x | | Q3 | 205.24 | 195.05 | -4.97% | 1.052x | | Q4 | 93.60 | 90.58 | -3.23% | 1.033x | | Q5 | 292.34 | 289.93 | -0.82% | 1.008x | | Q6 | 103.59 | 106.02 | 2.35% | 0.977x | | Q7 | 370.86 | 365.40 | -1.47% | 1.015x | | Q8 | 392.01 | 364.63 | -6.98% | 1.075x | | Q9 | 512.66 | 483.45 | -5.70% | 1.060x | | Q10 | 246.01 | 257.01 | 4.47% | 0.957x | | Q11 | 73.33 | 70.21 | -4.26% | 1.045x | | Q12 | 143.58 | 143.53 | -0.04% | 1.000x | | Q13 | 193.30 | 193.57 | 0.14% | 0.999x | | Q14 | 157.01 | 146.14 | -6.92% | 1.074x | | Q15 | 255.58 | 258.73 | 1.23% | 0.988x | | Q16 | 58.90 | 57.14 | -2.97% | 1.031x | | Q17 | 515.22 | 491.16 | -4.67% | 1.049x | | Q18 | 518.50 | 516.90 | -0.31% | 1.003x | | Q19 | 212.28 | 211.63 | -0.30% | 1.003x | | Q20 | 229.34 | 224.54 | -2.09% | 1.021x | | Q21 | 594.29 | 530.87 | -10.67% | 1.119x | | Q22 | 60.20 | 59.18 | -1.70% | 1.017x | </details> <details> <summary>TPCH SF10 default batch size, 32 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 294.06 | 286.80 | -2.47% | 1.025x | | Q2 | 110.59 | 103.55 | -6.37% | 1.068x | | Q3 | 227.86 | 215.08 | -5.61% | 1.059x | | Q4 | 110.99 | 102.77 | -7.41% | 1.080x | | Q5 | 347.34 | 319.49 | -8.02% | 1.087x | | Q6 | 109.39 | 109.91 | 0.47% | 0.995x | | Q7 | 423.98 | 385.42 | -9.09% | 1.100x | | Q8 | 428.83 | 384.00 | -10.45% | 1.117x | | Q9 | 559.81 | 510.72 | -8.77% | 1.096x | | Q10 | 269.17 | 265.02 | -1.54% | 1.016x | | Q11 | 85.99 | 80.21 | -6.72% | 1.072x | | Q12 | 153.67 | 150.36 | -2.15% | 1.022x | | Q13 | 197.90 | 188.72 | -4.64% | 1.049x | | Q14 | 161.28 | 153.93 | -4.55% | 1.048x | | Q15 | 259.92 | 261.01 | 0.42% | 0.996x | | Q16 | 64.90 | 63.70 | -1.85% | 1.019x | | Q17 | 574.18 | 531.76 | -7.39% | 1.080x | | Q18 | 572.23 | 538.68 | -5.86% | 1.062x | | Q19 | 227.95 | 220.19 | -3.41% | 1.035x | | Q20 | 232.25 | 225.80 | -2.78% | 1.029x | | Q21 | 622.54 | 579.94 | -6.84% | 1.073x | | Q22 | 62.29 | 61.06 | -1.98% | 1.020x | </details> <details> <summary>TPCH SF10 default batch size, 64 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 285.10 | 299.41 | 5.02% | 0.952x | | Q2 | 161.42 | 153.51 | -4.90% | 1.052x | | Q3 | 297.85 | 272.09 | -8.65% | 1.095x | | Q4 | 147.28 | 140.69 | -4.47% | 1.047x | | Q5 | 428.29 | 381.28 | -10.98% | 1.123x | | Q6 | 106.27 | 108.41 | 2.02% | 0.980x | | Q7 | 494.50 | 443.89 | -10.23% | 1.114x | | Q8 | 507.01 | 446.69 | -11.90% | 1.135x | | Q9 | 667.11 | 624.78 | -6.34% | 1.068x | | Q10 | 294.91 | 299.05 | 1.40% | 0.986x | | Q11 | 112.17 | 104.79 | -6.57% | 1.070x | | Q12 | 168.23 | 166.87 | -0.81% | 1.008x | | Q13 | 198.74 | 196.30 | -1.23% | 1.012x | | Q14 | 175.31 | 177.74 | 1.39% | 0.986x | | Q15 | 265.68 | 265.71 | 0.01% | 1.000x | | Q16 | 85.69 | 82.93 | -3.22% | 1.033x | | Q17 | 691.32 | 629.09 | -9.00% | 1.099x | | Q18 | 697.85 | 617.88 | -11.46% | 1.129x | | Q19 | 237.00 | 243.78 | 2.86% | 0.972x | | Q20 | 272.55 | 278.57 | 2.21% | 0.978x | | Q21 | 813.29 | 683.82 | -15.92% | 1.189x | | Q22 | 87.14 | 76.04 | -12.73% | 1.146x | </details> <details> <summary>TPCH SF10 default batch size, 300 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 277.84 | 304.08 | 9.45% | 0.914x | | Q2 | 1303.10 | 1268.65 | -2.64% | 1.027x | | Q3 | 1496.14 | 1393.15 | -6.88% | 1.074x | | Q4 | 681.20 | 652.85 | -4.16% | 1.043x | | Q5 | 1680.43 | 1469.91 | -12.53% | 1.143x | | Q6 | 100.65 | 105.75 | 5.07% | 0.952x | | Q7 | 1880.26 | 1652.83 | -12.10% | 1.138x | | Q8 | 1956.81 | 1760.72 | -10.02% | 1.111x | | Q9 | 1787.75 | 1454.84 | -18.62% | 1.229x | | Q10 | 1334.62 | 1296.02 | -2.89% | 1.030x | | Q11 | 1018.99 | 994.13 | -2.44% | 1.025x | | Q12 | 768.97 | 780.88 | 1.55% | 0.985x | | Q13 | 671.88 | 638.51 | -4.97% | 1.052x | | Q14 | 603.10 | 586.19 | -2.80% | 1.029x | | Q15 | 302.19 | 295.28 | -2.29% | 1.023x | | Q16 | 597.64 | 585.39 | -2.05% | 1.021x | | Q17 | 1963.57 | 1712.46 | -12.79% | 1.147x | | Q18 | 1942.46 | 1634.96 | -15.83% | 1.188x | | Q19 | 818.85 | 808.19 | -1.30% | 1.013x | | Q20 | 1499.39 | 1468.55 | -2.06% | 1.021x | | Q21 | 3006.35 | 2277.49 | -24.24% | 1.320x | | Q22 | 584.39 | 560.47 | -4.09% | 1.043x | </details> **Stress cases:** - These runs use `--batch-size 1024` to stress the repartition path. They are included to show the mechanism under smaller input batches and higher output fanout, not as the primary end-to-end performance claim. <details> <summary>TPCH SF10, 8 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 640.78 | 451.82 | -29.49% | 1.420x | | Q2 | 315.81 | 150.07 | -52.48% | 2.100x | | Q3 | 899.21 | 375.88 | -58.20% | 2.390x | | Q4 | 469.31 | 217.07 | -53.75% | 2.160x | | Q5 | 1131.37 | 446.36 | -60.55% | 2.530x | | Q6 | 376.40 | 163.66 | -56.52% | 2.300x | | Q7 | 1388.40 | 484.36 | -65.11% | 2.870x | | Q8 | 1369.67 | 571.62 | -58.27% | 2.400x | | Q9 | 1834.81 | 739.88 | -59.68% | 2.480x | | Q10 | 813.73 | 361.94 | -55.52% | 2.250x | | Q11 | 267.06 | 114.84 | -57.00% | 2.330x | | Q12 | 526.41 | 250.39 | -52.43% | 2.100x | | Q13 | 760.54 | 324.78 | -57.30% | 2.340x | | Q14 | 446.91 | 221.04 | -50.54% | 2.020x | | Q15 | 764.64 | 375.67 | -50.87% | 2.040x | | Q16 | 167.74 | 80.36 | -52.09% | 2.090x | | Q17 | 1801.72 | 763.58 | -57.62% | 2.360x | | Q18 | 3303.89 | 1649.87 | -50.06% | 2.000x | | Q19 | 694.16 | 354.97 | -48.86% | 1.960x | | Q20 | 693.91 | 323.17 | -53.43% | 2.150x | | Q21 | 3112.83 | 1065.36 | -65.78% | 2.920x | | Q22 | 205.88 | 95.97 | -53.38% | 2.150x | </details> <details> <summary>TPCH SF10, 16 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 518.84 | 328.66 | -36.66% | 1.580x | | Q2 | 350.47 | 148.64 | -57.59% | 2.360x | | Q3 | 1003.55 | 371.04 | -63.03% | 2.700x | | Q4 | 589.70 | 258.05 | -56.24% | 2.290x | | Q5 | 1343.64 | 506.01 | -62.34% | 2.660x | | Q6 | 322.21 | 130.93 | -59.37% | 2.460x | | Q7 | 1527.85 | 550.88 | -63.94% | 2.770x | | Q8 | 1476.46 | 578.77 | -60.80% | 2.550x | | Q9 | 2091.16 | 785.54 | -62.44% | 2.660x | | Q10 | 817.98 | 331.02 | -59.53% | 2.470x | | Q11 | 341.46 | 123.31 | -63.89% | 2.770x | | Q12 | 493.51 | 221.61 | -55.10% | 2.230x | | Q13 | 690.52 | 290.54 | -57.92% | 2.380x | | Q14 | 410.54 | 171.45 | -58.24% | 2.390x | | Q15 | 733.96 | 290.56 | -60.41% | 2.530x | | Q16 | 197.35 | 86.09 | -56.37% | 2.290x | | Q17 | 2089.12 | 828.96 | -60.32% | 2.520x | | Q18 | 2712.00 | 1097.77 | -59.52% | 2.470x | | Q19 | 602.77 | 260.74 | -56.74% | 2.310x | | Q20 | 661.20 | 288.58 | -56.35% | 2.290x | | Q21 | 5490.50 | 1151.50 | -79.03% | 4.770x | | Q22 | 198.38 | 103.13 | -48.01% | 1.920x | </details> <details> <summary>TPCH SF10, 32 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 533.86 | 338.54 | -36.59% | 1.580x | | Q2 | 439.59 | 199.50 | -54.62% | 2.200x | | Q3 | 1242.19 | 510.11 | -58.93% | 2.440x | | Q4 | 743.92 | 363.33 | -51.16% | 2.050x | | Q5 | 1711.97 | 666.50 | -61.07% | 2.570x | | Q6 | 325.39 | 134.07 | -58.80% | 2.430x | | Q7 | 1947.59 | 722.22 | -62.92% | 2.700x | | Q8 | 1914.31 | 775.62 | -59.48% | 2.470x | | Q9 | 2662.07 | 976.47 | -63.32% | 2.730x | | Q10 | 902.80 | 362.71 | -59.82% | 2.490x | | Q11 | 400.93 | 170.81 | -57.40% | 2.350x | | Q12 | 572.19 | 265.06 | -53.68% | 2.160x | | Q13 | 736.31 | 296.82 | -59.69% | 2.480x | | Q14 | 430.11 | 180.93 | -57.93% | 2.380x | | Q15 | 732.36 | 327.12 | -55.33% | 2.240x | | Q16 | 245.97 | 116.24 | -52.74% | 2.120x | | Q17 | 2711.18 | 1100.17 | -59.42% | 2.460x | | Q18 | 2946.70 | 1176.02 | -60.09% | 2.510x | | Q19 | 600.47 | 258.58 | -56.94% | 2.320x | | Q20 | 765.20 | 337.01 | -55.96% | 2.270x | | Q21 | 10062.70 | 1534.95 | -84.75% | 6.560x | | Q22 | 250.50 | 128.27 | -48.79% | 1.950x | </details> <details> <summary>TPCH SF10, 64 partitions, all queries</summary> | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q1 | 595.70 | 324.74 | -45.49% | 1.830x | | Q2 | 663.08 | 305.30 | -53.96% | 2.170x | | Q3 | 1744.90 | 727.81 | -58.29% | 2.400x | | Q4 | 1070.72 | 566.20 | -47.12% | 1.890x | | Q5 | 2447.07 | 938.91 | -61.63% | 2.610x | | Q6 | 315.47 | 132.73 | -57.93% | 2.380x | | Q7 | 2807.33 | 1004.83 | -64.21% | 2.790x | | Q8 | 2674.51 | 1069.64 | -60.01% | 2.500x | | Q9 | 3777.94 | 1424.08 | -62.31% | 2.650x | | Q10 | 1086.91 | 469.38 | -56.82% | 2.320x | | Q11 | 575.59 | 264.02 | -54.13% | 2.180x | | Q12 | 841.83 | 387.25 | -54.00% | 2.170x | | Q13 | 867.57 | 379.90 | -56.21% | 2.280x | | Q14 | 470.87 | 214.58 | -54.43% | 2.190x | | Q15 | 762.07 | 340.55 | -55.31% | 2.240x | | Q16 | 337.20 | 179.25 | -46.84% | 1.880x | | Q17 | 3953.82 | 1701.46 | -56.97% | 2.320x | | Q18 | 3763.51 | 1606.90 | -57.30% | 2.340x | | Q19 | 644.43 | 314.27 | -51.23% | 2.050x | | Q20 | 973.56 | 453.24 | -53.45% | 2.150x | | Q21 | 19356.91 | 2396.96 | -87.62% | 8.080x | | Q22 | 366.20 | 195.40 | -46.64% | 1.870x | </details> <details> <summary>TPCH SF10, 300 partitions, targeted high-fanout queries</summary> Yes this is a real use case for fanout in distributed-datafusion | Query | main ms | grouped ms | change | speedup | |---:|---:|---:|---:|---:| | Q3 | 2543.94 | 2250.91 | -11.52% | 1.130x | | Q9 | 6495.22 | 4755.78 | -26.78% | 1.370x | | Q10 | 1869.05 | 1709.18 | -8.55% | 1.090x | | Q13 | 1238.63 | 1157.47 | -6.55% | 1.070x | | Q15 | 461.51 | 446.25 | -3.31% | 1.030x | | Q21 | 37810.29 | 5594.01 | -85.21% | 6.760x | | Q22 | 1084.95 | 1058.74 | -2.42% | 1.020x | </details> <details> <summary>TPCH SF10, 300 partitions, peak RSS stress</summary> Measured with `/usr/bin/time -l`, one iteration, `--batch-size 1024`, `--partitions 300`, and no DataFusion memory limit. RSS is process peak resident set size from the OS. | Query | main ms | grouped ms | time change | main peak RSS | grouped peak RSS | RSS change | |---:|---:|---:|---:|---:|---:|---:| | Q7 | 5171.45 | 4151.15 | -19.73% | 3.69 GiB | 3.75 GiB | 1.61% | | Q9 | 6055.57 | 4758.10 | -21.43% | 4.01 GiB | 4.01 GiB | 0.04% | | Q21 | 36300.80 | 5810.14 | -83.99% | 2.96 GiB | 2.05 GiB | -30.79% | </details> #### Memory concern and follow-up work This PR changes output batches from materializing per-partition batches to slices of one reordered batch. This means sibling slices can share the same buffers. Potential concern: ```text one reordered batch allocation -> slice for partition 0 -> slice for partition 1 -> slice for partition 2 ``` A slow output partition can keep the shared reordered batch buffers alive until its slice is dropped. Also, `RecordBatch::get_array_memory_size()` may count shared slice buffers repeatedly when repartition reserves memory per output batch. The peak RSS stress above did not show a process-memory regression in the measured queries. Follow-up work should add buffer-aware accounting. ## Are there any user-facing changes? <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> No. <!-- If there are any breaking changes to public APIs, please add the `api change` label. -->
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